Today’s work processes increasingly suffer from painful frictional losses resulting from the immense number of business processes, solution models and objectives. Over the course of time, proprietary methods have developed for various tasks, each of which, in turn, meets its own specific requirements. What is missing, however, is the synergetic potential to create a large entity through the cooperation and combination of the originally individual processes, which increases flexibility and efficiency. This can be achieved through the consistent use of APIs. Coordinated processes as an efficiency tool The use of APIs to increase efficiency and flexibility is not primarily aimed to increase revenue directly. This aspect is already indirectly achieved with consistent application. Above all, it is important in this area to minimise resistance forces and avoidable resource consumption in order to achieve greater economic efficiency in this way. More information on aspects of economic efficiency when using APIs can be found in the article Economic benefits of APIs. In the area of software development, the use of APIs allows the creation of a universal tool tailored to individual needs that provides related business processes and services side by side. A large part of the efficiency losses observed in the company is due to the constant switching between the required applications - a configuration that prevents any flexible response to current or time-critical events right from the start. APIs create a common basis Here APIs can help in two ways. On the one hand, they unite all applications required for the task under a common user environment. On the other hand, the internal structure of APIs allows flexible adaptation to current conditions. The benefits of this strategy are spectacular: APIs not only allow previously separate applications to be efficiently combined into a single functional unit, but they also enable rapid and problem-free expansion with additional functionalities. Regardless of how many individual applications cooperate with each other - access to them is always simple and highly effective. APIs as a tool for flexible data management A coordinated application environment consisting of several jointly operating applications requires the uncomplicated and fast administration of all necessary data as well as flexible access to it. APIs make data sharing effortless, allowing universal access that is essential for collaborative or time-critical processes. The demand for simple tools to change or extend application functionality, which is associated with flexible data management, is also fully met by APIs. They open up effortless and user-friendly ways for efficient and flexible data exchange with customers and business partners, combined with seamless access to all necessary backend processes. APIs as a bridge between developers and users The special data structure of APIs allows particularly intensive and fast communication channels between software developers and end users or marketing professionals involved in business processes. This enables optimized strategies to respond very quickly to changing market conditions or other external influences. Conclusion In all phases of the operational value chain, APIs can achieve often dramatic efficiency gains and noticeable process flexibility. This ranges from conceptual design to administration and usage. APIs support the development of new products and processes as well as the optimization of existing resources. When networking with cooperating systems, accessing data in real time and eliminating loss of time, the use of APIs is a must.

API-Economy: With API products to new sources of revenue The tremendous success of APIs in recent years has opened up completely new perspectives for developers. More and more companies are realizing the immense economic and organizational benefits of an API-based software architecture. The next step was foreseeable: APIs became API products, tailored to the individual needs of customers. For companies, this means concentrating on the essentials. For developers of API products, it means the emergence of a new, lucrative market. API products are digital competence API-Economy, the economic sector that deals with the development and distribution of API products, is based on a simple but captivating insight: Not everyone can know everything. Acquiring the additional skills needed for your own business model takes time, money and resources. Since the development of new business areas usually requires a number of new competences, the effort multiplies with each additional competence - an effort that in many cases does not pay off. The alternative would be to simply purchase the missing competence. This is the moment when APIs come into the picture. From the API to the API product In simple terms, APIs are interfaces that enable software to access specific functionalities of other applications. In other words, the software uses the expertise it has been given through the API without having its own program code describing that expertise. The problem with this is that the API usually provides only one special competence. In order to cope with complex tasks in companies, however, combinations of different competencies are usually required, which must be precisely coordinated with each other. This task is fulfilled by API products, i.e. the combination of different APIs for different parts of the task. The individual APIs must not only fulfil their special tasks, but must also communicate optimally with the other APIs in order to interact smoothly in the interest of the target. Developers of API products have two options to create a custom API product: Either all APIs contained in the product originate from own development or the API product consists of specially coordinated, already existing APIs. In many cases, combinations are also possible: Competences for which third-party APIs already exist are served by these. All others require the development of new APIs. The product then consists of existing and new APIs, which are optimally adapted to each other. There are no limits to special functions In particular, the combination of third-party APIs and self-programmed APIs opens up undreamt-of possibilities for developers to design individual applications for the respective customer. Solutions are conceivable that target API products for internal use within the company or those that are designed as part of the business model for use by corporate customers. In this way, differentiated soft limits can be implemented, such as throttling, in order to limit the number of accesses within a certain period of time. These and other functionalities can be integrated into the API product exactly according to the customer’s individual requirements. When it comes to pricing, the developer has every option open to him - from price per query to graduated prices for different expansion stages and flat solutions. In addition, price models based on special application scenarios are conceivable. Conclusion API products are the answer to the problem of companies generating additional competencies with justifiable effort. For developers, API products represent a virtually inexhaustible new market in which they provide companies with the skills they need through tailored solutions.

Swagger is an open-source framework that simplifies the creation, description, and documentation of APIs. An API documentation provides detailed information on how an API works, which endpoints it offers, and how developers can interact with it. It includes details about HTTP methods, request and response formats, and authentication mechanisms. Originally developed by SmartBear Software, Swagger was later incorporated into the OpenAPI standard. Using a YAML- or JSON-based specification file, developers can define their APIs in a standardized manner. Swagger tools, including Swagger UI and Swagger Editor, allow for a visual representation of API documentation and interactive testing. This accelerates the development process and improves API quality. Why is Swagger Useful? Benefits for Developers Developers benefit significantly from Swagger as it automates the documentation of their APIs, reducing manual effort. Since API specifications are provided in a standardized format, team collaboration becomes much more efficient. Additionally, Swagger enables early detection and resolution of errors, greatly improving code quality. Another advantage is support for multiple programming languages, including Java, Python, and JavaScript, making Swagger highly versatile. Benefits for Testers Testers also benefit from Swagger, as it allows them to call and test API endpoints directly without needing additional software. They can systematically analyze API responses and error codes to identify potential issues early. The ability to create automated test cases and integrate them into test frameworks significantly simplifies quality assurance. Benefits for Businesses Companies also gain substantial advantages from using Swagger. The ability to document APIs in a standardized manner improves clarity and simplifies integration. This reduces the training effort for new developers and facilitates collaboration with partners and customers. In scalable systems, Swagger ensures easier maintenance, allowing APIs to be updated and extended without requiring extensive changes to documentation. Benefits for Partners Businesses providing APIs to external partners benefit from clear and standardized documentation through Swagger. Partners can more easily access existing API functions and integrate them into their own applications. This facilitates the development of new digital services and fosters innovation by enabling seamless connections between different platforms. Moreover, well-documented APIs enable faster implementation of new features and reduce support efforts, as partners can directly access understandable specifications and testing capabilities. Common Use Cases for Swagger APIs are a crucial part of modern software development and must be effectively documented, tested, and managed. Swagger is used in various scenarios to make working with APIs more efficient. REST API Documentation Many developers use Swagger to create clear and comprehensible documentation for REST APIs. Especially in web applications and microservices, a well-structured API description is essential to help other developers understand and use the API effectively. With Swagger, API endpoints can be clearly defined and documented, making it easier for users to understand how the interface works. API Testing and Error Analysis Beyond documentation, Swagger is also used in the testing process. Testers can validate API endpoints and analyze responses directly using Swagger UI. This facilitates early detection of errors and incompatibilities. In complex systems where multiple APIs interact, an efficient testing environment is crucial to quickly identify and resolve issues. Automatic Code Generation Another key use case for Swagger is automatic code generation. Developers can generate client libraries and server stubs from an API specification using Swagger. This not only saves time during implementation but also ensures a uniform code base that is easier to maintain. Companies frequently use this feature to accelerate the development of new applications and provide standardized API interfaces. Integration into DevOps Processes In DevOps environments, Swagger plays a central role as it can be integrated into CI/CD pipelines. This ensures that APIs are always up-to-date and correctly documented. Continuous validation of the API specification helps ensure that changes and extensions to the API are immediately reflected in the documentation. This significantly improves collaboration between developers, testers, and operations teams. Security Policies and API Management Businesses also use Swagger for defining security policies and managing APIs. This includes implementing authentication mechanisms such as OAuth 2.0 or API keys, setting access restrictions for different user groups, and monitoring API requests to detect suspicious activity. These measures help protect sensitive data and ensure compliance with industry-specific security standards. A well-documented API allows for more precise control over permissions and access restrictions, improving security management. Large companies managing multiple APIs particularly benefit from Swagger’s support in maintaining security standards. Difference Between Swagger and OpenAPI Although the terms Swagger and OpenAPI are often used interchangeably, there are some differences. Swagger was originally developed as a suite of API documentation tools, while OpenAPI is now the official standard for describing REST APIs, managed by the OpenAPI Initiative. While OpenAPI serves as the specification framework, Swagger provides various tools to create, test, and visualize OpenAPI specifications. Many businesses now adopt OpenAPI as their standard due to its compatibility with multiple platforms and broader support. Practical Use of Swagger Many companies use Swagger as part of a global API-first strategy. In an API-first environment, API definitions are created at the beginning of the development process. Instead of documenting APIs retroactively, they are initially specified using tools like Swagger. These specifications then serve as the foundation for developers who build services and applications based on them. Large tech companies and SaaS providers use Swagger to provide consistent and standardized API documentation. By defining APIs early on, development teams can work independently while following a reliable interface description. This leads to more efficient development and simplifies the integration of APIs into various systems. Furthermore, Swagger plays a crucial role in collaboration with external partners and customers. Companies offering public or partner APIs use Swagger to create interactive API documentation. This allows external developers to test API endpoints directly without needing additional code. It lowers the barrier to using new APIs and enhances the developer experience. Another practical example is Swagger’s use in regulatory compliance. Industries such as finance and healthcare are subject to strict data exchange regulations. Here, Swagger helps define APIs clearly and ensures that all endpoints are properly documented and verifiable. This simplifies regulatory compliance and facilitates audits. Conclusion Swagger has become an indispensable tool in modern API development. It not only enables efficient documentation and validation of APIs but also supports automation and standardization in development processes. Developers benefit from standardized documentation and the ability to test and refine APIs directly. Companies can optimize their API-first strategies with Swagger, improving team collaboration and reducing time-to-market for new products.

What is a Swagger API? Swagger is one of the most well-known open-source frameworks for describing, documenting, and developing RESTful APIs. It provides a standardized method for API specification, making it easier for professionals to create and manage interfaces. With Swagger, API endpoints can be visually represented, tested, and well-structured documentation can be generated. This significantly improves collaboration between professionals, testers, and other stakeholders. Originally, Swagger was developed as a standalone framework before evolving into the OpenAPI Specification (OAS). Today, OpenAPI serves as the standard for precisely defining and documenting APIs. Swagger remains an essential tool for the efficient development and documentation of modern APIs. Why is Swagger Used? Swagger offers numerous benefits for professionals and organizations. One of its greatest advantages is the automatic generation of interactive API documentation. This allows professionals to efficiently utilize API interfaces without manually writing documentation. Instead of laboriously testing API calls, they can be tested directly in the browser using Swagger UI—without requiring additional tools. This saves time and optimizes development. A typical use case is documenting microservices architectures, where many small, independent services need to be efficiently described and tested. Another advantage is the improved collaboration within teams. Since a clearly defined API specification is available, backend and frontend development teams can work in parallel. Support for multiple programming languages and the ability to generate code helps professionals quickly create client SDKs and server stubs. This automation reduces errors and accelerates the overall development process. What is Swagger Particularly Well-Suited For? Swagger is widely used for the efficient development, documentation, and testing of REST APIs. By providing a unified API specification, communication between teams is simplified, as all stakeholders have a common foundation for API development. Additionally, it helps identify errors early, as APIs can be validated and tested even in the planning phase. Swagger is particularly advantageous for microservices architectures, where many small, independent services interact. In such scenarios, clear and understandable API documentation is essential. Organizations that follow an API-First approach also benefit greatly from Swagger. Instead of documenting APIs after implementation, the API specification is defined right from the start. This ensures that all stakeholders have a consistent understanding of the API before development begins. Additionally, integrating third-party services is significantly simplified due to clear documentation. What Does the Contract/API-First Approach Mean? An important approach in modern API development is the Contract/API-First principle. Here, the API specification is created first before implementation begins. This offers numerous benefits, particularly for large, distributed teams. A clearly defined API serves as a contractual basis for all stakeholders. This not only simplifies planning and coordination but also enables parallel development of frontend and backend components. Using Swagger as an API-First tool significantly facilitates code generation. Professionals can automatically generate client and server code, accelerating implementation and minimizing errors. An API-First approach also ensures that APIs are well thought out, consistent, and comprehensible, thereby improving overall software quality. What Are the Differences Between Swagger 2.0 and OpenAPI 3.0? With the evolution of Swagger, OpenAPI 3.0 was introduced, bringing several significant improvements over Swagger 2.0. One of the biggest changes concerns the structure of API documentation. OpenAPI 3.0 allows for a more flexible definition of endpoints and data models. It also supports OneOf, AnyOf, and AllOf, making it easier to implement complex schema definitions. Another major difference is the improved support for HTTP methods and content types. While Swagger 2.0 only supported a single producing or consuming type per operation, OpenAPI 3.0 allows for the detailed specification of multiple media types within an API definition. Additionally, the handling of parameters and request types has been optimized, especially regarding support for JSON Schema. An additional feature of OpenAPI 3.0 is the enhanced support for server-side configurations. The new version allows for the definition of multiple server URLs, enabling APIs to be used flexibly across different environments. This makes it easier for professionals to switch between development, testing, and production environments. Is Swagger Still Used Today? Swagger remains one of the most widely used API documentation tools. Although the term "Swagger" is increasingly being replaced by "OpenAPI," many original Swagger tools are still in use. The community continues to grow, and numerous organizations rely on Swagger to optimize their API development. Thanks to broad support and continuous development, Swagger remains an indispensable tool for professionals and organizations looking to develop and document modern APIs. Conclusion Swagger provides a powerful solution for API development and documentation. With its extensive features, ease of use, and broad support, it remains a key tool for professionals and organizations. Particularly within an API-First approach, Swagger proves to be highly valuable, enabling efficient planning, specification, and implementation of APIs. Anyone looking to create a well-documented and easily testable REST API will find Swagger to be an essential tool.

Installation and Setup of Swagger Swagger is a powerful open-source tool for API documentation. It is used for the structured description, visualization, and interaction with APIs. Developers benefit from clear, interactive documentation that significantly facilitates the use and maintenance of APIs. With Swagger, API specifications can be comprehensively captured and displayed, providing an accurate reflection of the current state of an API. This not only promotes traceability, but also eases collaboration between developers. Before using Swagger, it must be installed and configured according to the technology stack, with various integration options available. Installation Depending on the technology stack, there are different ways to integrate Swagger. The most common options are: Swagger UI, a user interface for visualizing and interacting with API documentation. It can be integrated via a CDN or locally, providing an interactive view of the API. Swagger Editor, an online editor that allows you to write and test API specifications directly. This greatly simplifies the creation and customization of documentation. Swagger Codegen, a tool for generating API client libraries and server stubs from a Swagger specification. This enables support for various programming languages and facilitates automatic code generation. Swagger for various frameworks, such as: Node.js (Express.js): Installation with npm install swagger-ui-express Spring Boot (Java): Integration with springfox-swagger2 Python (Flask): Using flasgger Setup After installation, Swagger must be integrated into the project. The integration depends on the environment used. In an Express.js application, the integration looks, for example, as follows: const swaggerUi = require('swagger-ui-express'); const swaggerDocument = require('./swagger.json'); const app = require('express')(); app.use('/api-docs', swaggerUi.serve, swaggerUi.setup(swaggerDocument)); app.listen(3000, () => console.log('Server is running on port 3000')); Once the application has started, the API documentation can be accessed in the browser at http://localhost:3000/api-docs. There, all endpoints are clearly displayed and can be tested interactively. Creating Swagger API Endpoints: First Steps To document an API with Swagger, a Swagger 2.0 specification must be created. This can be written in YAML or JSON and describes the API endpoints in detail. In doing so, not only are the available routes defined, but also the expected parameters and response structures are specified. A simple example of an API endpoint could look as follows: swagger: '2.0' info: title: Example API description: A simple API to demonstrate Swagger version: 1.0.0 host: localhost:3000 schemes: - http paths: /users: get: summary: Retrieve list of all users produces: - application/json responses: '200': description: Successful response schema: type: array items: type: object properties: id: type: integer name: type: string Components: Reusable Definitions Swagger enables the reuse of components such as schemas, parameters, and responses to ensure a consistent and maintainable API documentation. The components section in OpenAPI 3.0 corresponds to the definitions section in Swagger 2.0. An example of reusing definitions: swagger: '2.0' info: title: API with Reusable Components version: 1.0.0 host: localhost:3000 schemes: - http definitions: User: type: object properties: id: type: integer name: type: string paths: /users: get: summary: Retrieve list of all users produces: - application/json responses: '200': description: Successful response schema: type: array items: $ref: '/definitions/User' Here, the User schema is defined in the definitions section and then reused in the response of the /users endpoint. Changes to this schema affect all endpoints that reference this definition, thereby maintaining consistency. However, modifications should be made with caution to avoid unexpected impacts on existing API clients. This approach ensures better maintainability, as changes need to be made in only one place. Security: API Authentication and Authorization A well-secured API is essential to prevent unauthorized access. It is important to distinguish between authentication and authorization. Authentication ensures that a user or system is indeed who they claim to be (e.g., via API keys or OAuth2), while authorization determines which actions an authenticated user is allowed to perform (e.g., read or write permissions). Swagger 2.0 supports various authentication methods, including API keys, OAuth2, and Basic Authentication. An example of an API secured with an API key: swagger: '2.0' info: title: Secured API version: 1.0.0 host: localhost:3000 schemes: - http securityDefinitions: ApiKeyAuth: type: apiKey in: header name: X-API-Key paths: /secure-data: get: summary: Retrieve secured data security: - ApiKeyAuth: [] responses: '200': description: Successful response schema: type: object properties: data: type: string OAuth 2.0 Authentication A modern and flexible method for authentication is OAuth 2.0. It allows users to securely authenticate with the API. securityDefinitions: OAuth2: type: oauth2 flow: accessCode authorizationUrl: https://example.com/oauth/authorize tokenUrl: https://example.com/oauth/token scopes: read: Access to secured resources paths: /user-info: get: summary: Retrieve user information security: - OAuth2: - read responses: '200': description: Successful response schema: type: object properties: username: type: string This ensures that the /user-info endpoint is only accessible to authenticated users with the corresponding OAuth2 token. is accessible. The scope read allows users to access protected resources read access to protected resources without making any changes. This is suitable for endpoints that provide sensitive but unchangeable information, such as such as profile data or system status. An example of an API secured with an API key: swagger: '2.0' info: title: Secured API version: 1.0.0 host: localhost:3000 schemes: - http securityDefinitions: ApiKeyAuth: type: apiKey in: header name: X-API-Key paths: /secure-data: get: summary: Retrieve secured data security: - ApiKeyAuth: [] responses: '200': description: Successful response schema: type: object properties: data: type: string Best Practices for Well-Structured API Documentation To design optimal API documentation, several best practices should be followed: Consistent Structure: Well-organized API documentation facilitates understanding and ensures uniform documentation of all endpoints. This can be encapsulated in the form of API design guidelines, which, among other things, establish conventions for naming, versioning, and security aspects. Descriptive Details: Each endpoint should include detailed descriptions so that users can immediately understand how it works. For example, the /users endpoint might be accompanied by the description Returns a list of all registered users. Optionally, it can be filtered by specific names using a query parameter. This helps developers better understand the purpose and potential applications of the endpoint. Provide Sample Data: By using example or examples, a realistic impression of API responses can be conveyed. For instance, an endpoint that returns user information could include a sample response with id: 1 and name: 'John Doe' to illustrate the expected data structure. Specify Authentication: If authentication is required, it should be clearly documented, for example by using API keys or OAuth. API keys are easy to implement and are well-suited for server-side applications, but they can be insecure if exposed in client applications. OAuth provides a more secure authentication mechanism with token-based access, though it is more complex to implement and requires additional infrastructure such as an authorization server. Version Control: An API evolves over time. Clear versioning ensures that users are always using the correct documentation. For instance, an API version can be defined in the URL (e.g., /v1/users) or through the info.version attribute in Swagger (e.g., version: '1.0.0'). This helps to support older versions and introduce new features gradually. Using Semantic Versioning (SemVer) (MAJOR.MINOR.PATCH) enables developers to communicate changes transparently, for example, an increase in the major version (e.g., v2.0.0) indicates breaking changes, while minor updates (e.g., v1.1.0) add new features without breaking changes. Utilize Reusable Components: Frequently used elements such as schemas, parameters, or responses should be stored in definitions (in Swagger 2.0). This makes the API documentation more consistent and easier to maintain. Swagger allows for various types of definitions, including definitions for data models, parameters for reusable parameters, responses for predefined API responses, and securityDefinitions for authentication. For example, a user structure can be defined once and referenced multiple times: $ref: '/definitions/User'. Use an Interactive Swagger UI: An interactive documentation makes it easier for developers to test the API and reduces the communication overhead. Conclusion With these steps and proven methods, a professional API documentation using Swagger 2.0 is achievable. Well-maintained and well-structured API documentation not only facilitates implementation for developers but also improves collaboration with other teams, promotes maintainability, and increases the transparency of API usage. A well-structured documentation is an essential component of any API development, as it not only assists developers but also enhances team collaboration.

What is an API Definition? The API definition describes the structure and behavior of an API. It specifies which endpoints are available, which requests and responses are expected and which authentication methods must be used. A clearly defined API facilitates implementation and integration into existing systems, improves security and promotes code reusability. An API (Application Programming Interface) is an interface that allows different software applications to communicate with each other. APIs are a central component of modern software development and are used in numerous areas, including payment services, social media integrations and cloud computing. Different API Definitions and Their Use Cases APIs can be distinguished not only by their architecture, but also by the standards used for the definition and documentation of their interfaces. The choice of an API definition influences how developers design, document and implement APIs. Among the best-known standards are OpenAPI Specification (OAS), Swagger 2.0, RAML (RESTful API Modeling Language) and AsyncAPI. OpenAPI Specification (OAS) is currently the most widely used standard for describing RESTful APIs. It enables a machine-readable specification that can be used as a basis for generating code, documentation and tests. OAS facilitates API development by providing a consistent and comprehensible structure for the API definition. Swagger 2.0 was the predecessor of OAS and significantly contributed to the spread of standardized API definitions. With Swagger, developers can create interactive API documentation and test APIs directly. Although OAS is now the official standard, Swagger 2.0 is still used in many existing systems. RAML (RESTful API Modeling Language) is an alternative method for defining RESTful APIs. In contrast to OAS, RAML places a stronger focus on the reusability of API components and offers a clear, human-readable syntax. Developers often use RAML to design APIs in a structured manner before they are implemented. AsyncAPI is specifically designed for asynchronous APIs that are based on event-driven architectures. This standard is used especially for message queues, IoT platforms and microservices. AsyncAPI allows developers to define and document complex real-time communication, thereby enabling applications to be designed efficiently and in a scalable way. Important Components of an API Definition An API consists of several fundamental components that determine its functionality and enable interaction between systems. In this context, endpoints, requests and responses as well as authentication play a crucial role. Endpoints Endpoints are the specific access points of an API through which external applications can access the provided functions. They consist of a URL and define which data is available and how it can be retrieved or manipulated. For example, an endpoint for user management could be accessible at /api/users in order to retrieve or update user information. Requests and Responses Communication between client and server takes place via requests and responses. A client sends a request to an API endpoint, which typically includes an HTTP verb such as GET, POST, PUT or DELETE. The server processes the request and returns a response, which is usually in JSON or XML format. A successful request delivers an appropriate status code (e.g., 200 OK), whereas erroneous requests generate error codes such as 400 Bad Request or 404 Not Found. Business Types and Components In the modeling of API definitions, business objects play a central role. These are often defined by Business Types and Components in order to create reusable and consistent data structures. Business Types are abstracted data types that represent frequently used entities within a system. Examples are User'', Order'' or ``Invoice''. These types help to maintain a consistent structure across different endpoints. Components are reusable API building blocks that are used in definitions such as OpenAPI. They include, for example, schema definitions for data objects, security mechanisms and parameters. By using components, API specifications can be made modular and maintenance-friendly. Best Practices for Modeling an API Definition A well-structured API definition is crucial for efficient development and long-term maintainability. The following best practices help to design APIs that are consistent, comprehensible and extensible. Best Practices for Endpoints The following recommendations help to structure API endpoints clearly, enable efficient communication and ensure uniform usage. Ensure consistent naming: Endpoints should be named clearly, predictably and uniformly. For example, the resource for users should be accessible at /api/users instead of using unclear or different designations such as /api/getUsers or /api/userList. Implement versioning: An API should use versioning from the beginning in order to manage future changes cleanly. For example, /api/v1/users can be used for the first version of the API, while later iterations can run under /api/v2/users without interrupting existing integrations. Use HTTP methods correctly: Using the correct HTTP methods facilitates understanding and usage of the API. GET should be used for retrieving data, POST for creating new resources, PUT for updating and DELETE for removing data. Do not create unnecessary endpoints: Each endpoint should serve a clear function. Instead of creating a new endpoint for every single action (/api/getUsers, /api/updateUser, /api/removeUser), a generic structure should be used that consolidates CRUD operations (GET /api/users, PUT /api/users/{id}, DELETE /api/users/{id}). Offer filtering and pagination: In order to increase efficiency and make large data sets more manageable, endpoints should support options for filtering (/api/users?role=admin) and pagination (/api/users?page=1&limit=20). Best Practices for Requests and Responses The following recommendations help to structure API endpoints clearly, enable efficient communication and ensure uniform usage. Use status codes correctly: Every API should use standardized HTTP status codes for its responses in order to ensure an unambiguous interpretation. For example, 200 OK signals that the request was successful, whereas 201 Created confirms a newly created resource. Erroneous requests should be clearly identifiable by means of informative status codes such as 400 Bad Request (invalid input) or 404 Not Found (non-existent resource). Use uniform and well-structured data formats: JSON is the preferred format for modern APIs because it is easily readable and can be processed efficiently. A consistent schema should be maintained in order to make the structure understandable. For example, an API for users should always deliver the same JSON format: { "id": 1, "name": "Max Mustermann", "email": "max@example.com" } Provide detailed error messages: Instead of returning merely a generic 400 Bad Request error, the API should inform the client exactly why a request has failed. For example: { "error": "Invalid email format", "field": "email", "suggestion": "Please provide a valid email address." } This makes it easier for developers to debug errors and improves the user experience. Enable pagination and limitation of large data sets: APIs that return large data sets should implement mechanisms for pagination and filtering. For example, an API could support the following query: GET /users?page=2&limit=20 This ensures that the response does not become unnecessarily large and that the server is not overloaded. Use caching to improve performance: Frequently used data should be cached to reduce unnecessary API requests. By setting cache-control headers, the server can inform the client how long a response may be cached: Cache-Control: max-age=3600, public This improves loading times and reduces server load. Best Practices for Business Types and Components The following recommendations help to structure API endpoints clearly, enable efficient communication and ensure uniform usage. Uniform and comprehensible naming: Names for Business Types should be clear, descriptive and consistent. Instead of cryptic or abbreviated designations such as CustOrd1, a comprehensible notation such as CustomerOrder should be used. This facilitates readability and reduces misunderstandings, especially in larger development teams or when integrating with other systems. Ensure reusability: An API should be designed in such a way that its components can be used multiple times, in order to avoid redundancies and improve maintainability. For example, an Address schema can be used equally for users, companies and suppliers. Instead of creating separate address models for each entity (UserAddress, CompanyAddress), a generic Address schema should be implemented that can be used flexibly in different contexts. This not only facilitates the maintenance of the API, but also reduces inconsistencies in data processing. Use standardized types: In order to ensure a consistent and interoperable API, standardized data types should be used. For example, UUIDs (Universally Unique Identifiers) are ideal for unique identifiers because they ensure that each entry receives a unique and unpredictable ID. For date and time indications, the ISO 8601 standard (YYYY-MM-DDTHH:MM:SSZ) should be used, as it is internationally understandable and compatible with most programming languages. This prevents interpretation errors, especially in systems that operate with different time zones. Likewise, ISO 4217 for currency codes and ISO 3166-1 alpha-2 for country codes can be used to ensure uniformity. Best Practices for Authentication and Authorization The following recommendations help to structure API endpoints clearly, enable efficient communication and ensure uniform usage. Use OAuth 2.0 for secure authentication: OAuth 2.0 is a widely used and secure standard for authorization that enables flexible access control. It supports various grant types, including the Authorization Code Flow for web applications and the Client Credentials Flow for server-side applications. By using OAuth 2.0, APIs can ensure that only authorized clients gain access to protected resources. A frequently used extension protocol is OpenID Connect (OIDC), which enables identity verification with standardized user information.. Use JWTs to avoid server-side sessions: JSON Web Tokens (JWTs) enable secure and efficient authentication without the need for server-side sessions. A JWT consists of three parts: header, payload and signature, which together provide an encrypted and signed method for verifying a user’s identity. JWTs are particularly useful for scalable applications because they function as stateless tokens and reduce the overhead of centralized session management. However, they should always be provided with short expiration times (the exp claim) and stored securely, for example in HTTP-only cookies, to avoid attacks through token theft. Never pass tokens in URLs, but set them in the Authorization header: Transmitting tokens in URLs carries significant security risks because URLs can be stored in browser histories, server logs and referrer headers. Instead, tokens should always be transmitted securely in the Authorization header: Authorization: Bearer <token> This method ensures that tokens are not inadvertently exposed or intercepted by attackers. In addition, the API should be configured so that it communicates only over secure HTTPS connections to prevent man-in-the-middle attacks. Conclusion These API definitions play a crucial role in modern software development. They not only enable consistent documentation and development, but also seamless integration into various tools and frameworks. The choice of the right standard depends on the specific requirements of the respective project.