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    What Are API Documentation Tools? 

    API documentation tools are software used to create and manage documentation for application programming interfaces (APIs). These tools help explain an API’s functionalities, enabling developers and users to understand how to implement and use the API. 

    With the increasing complexity of APIs, tools that assist in generating clear and concise documentation have become crucial in ensuring that developers can quickly get up to speed without diving into the source code or requiring extensive support.

    These tools often provide features, including automation in documentation creation, support for different API types, and integration with version control systems. They aim to simplify the documentation process, making it easier for developers to update, share, and collaborate on API docs.

    This is part of a series of articles about code documentation.

    Key Features of API Documentation Tools 

    API documentation tools typically offer the following capabilities.

    Automatic Documentation Generation

    Many API documentation tools allow developers to generate documentation directly from code comments or annotations. By parsing code, these tools can automatically create a structured and readable documentation output, ensuring that the documentation stays up-to-date with the actual codebase. This eliminates discrepancies between the code and its documentation, a common issue in manual documentation processes.

    Searchable and Well-Organized Structure

    Having a searchable and well-organized documentation structure is essential for efficiency. API documentation tools often include search functionalities that allow users to quickly find specific functions or endpoints they need to reference. This feature saves time and makes the documentation more user-friendly, especially in extensive projects with multiple API endpoints or complex hierarchical structures.

    Version Control and Documentation for Multiple Versions

    Version control enables the management of documentation across different API versions. This is crucial for projects maintaining several API versions due to changing requirements or backward compatibility issues. With version control, developers can ensure that users can access the documentation relevant to the API version they’re implementing, avoiding confusion and potential integration problems.

    Markdown Support

    Markdown support enables easier formatting and writing of documentation. Many API documentation tools allow developers to write documentation in a plain text format that can be easily converted to rich text. Markdown’s simplicity encourages more frequent updates and adjustments to documentation, as it does not require complex formatting languages.

    Support for Multiple API Types

    APIs can vary significantly, including RESTful, GraphQL, SOAP, and more. Tools that support multiple types ensure flexibility and adaptability for developers working across different technologies. This versatility is crucial in diverse tech environments, enabling teams to use one tool for various projects without switching between different documentation platforms.

    Related content: Read our guide to code documentation standards

    Tips from the expert

    Omer Rosenbaum
    Omer Rosenbaum
    CTO and Co-founder @ Swimm
    1.
    Invest in API design-first tools: Start your API journey with design-first tools like Stoplight or Apidog. These allow you to create a well-structured specification before coding begins, reducing design errors and ensuring a strong foundation for both the API and its documentation.
    2.
    Implement a “Docs-as-code” approach: Treat your documentation as part of the codebase. Use version control (e.g., GitHub) to manage updates, track changes, and collaborate on docs with your dev team. This will ensure that your documentation evolves in lockstep with your API’s development.
    3.
    Incorporate live API examples: Tools that support “try it out” functionality (e.g., ReDocly, Apidog) allow users to interact with the API directly from the docs. This provides an invaluable hands-on experience for developers, leading to faster adoption and fewer support queries.

    Notable API Documentation Tools 

    1. OpenAPI Generator

    OpenAPI Generator is a tool that automates the generation of API clients, server stubs, and documentation from OpenAPI 2.0 and 3.x documents. By supporting multiple languages and technologies, OpenAPI Generator helps developers and API maintainers quickly generate code and documentation, reducing manual effort and speeding up the development process. 

    License: Apache-2.0

    Repo: https://github.com/OpenAPITools/openapi-generator

    GitHub stars: 21k+

    Contributors: ~3000

    Key features of OpenAPI Generator:

    • Client code generation: Generates client libraries in over 50 languages and frameworks, making it easy to create code that interacts with any server exposing an OpenAPI document. API maintainers can also automatically generate and distribute SDKs for their APIs.
    • Server stub generation: Creates server stubs in more than 40 languages and technologies, including Java, Kotlin, Go, and PHP. Some generators offer inversion of control (IoC) support, enabling developers to iterate on API designs without disrupting the underlying domain logic.
    • Schema and config generators: Automates the creation of database schemas and configurations with specialized generators, including those for MySQL, GraphQL, and Apache2 configurations. These can be customized and extended to fit project needs.
    • API documentation generation: Automatically converts OpenAPI metadata into readable documentation formats like HTML and Confluence Wiki (Cwiki). Supports converting OpenAPI 2.0 documents into the newer OpenAPI 3.x format for broader compatibility and improved features.
    • Customization: Uses Mustache-based templates that can be replaced or customized, giving developers full control over the structure and behavior of the generated code and documentation.

    2. Read the Docs

    Read the Docs is a platform for automating the building, hosting, and deployment of API documentation. It allows developers to maintain API docs using the same tools and workflows they use for code, ensuring that documentation stays current with every update. With built-in versioning, search, and integration with popular platforms like GitHub and GitLab, Read the Docs simplifies API documentation management.

    License: MIT

    Repo: https://github.com/readthedocs/readthedocs.org

    GitHub stars: ~8k

    Contributors: 400+

    Key features of Read the Docs for API Documentation:

    • Docs as code: Allows users to write and manage API documentation using their preferred editor and track changes with version control. 
    • Automatic documentation builds: Automatically rebuilds and publishes API documentation whenever changes are made in the repository, eliminating the need for manual updates.
    • API versioning: Supports multiple versions of API documentation, allowing users to access the correct version based on branches, tags, or commits.
    • Preview API changes: Shows previews of updates to API documentation in pull requests, helping users catch errors and verify changes before making them live. This feature integrates directly with GitHub and GitLab.
    • Comprehensive hosting: Manages the full deployment of API documentation, including hosting, authentication, and integrated search.

    Source: Read the Docs

    3. ReDocly

    ReDocly is an API platform to accelerate API adoption and innovation. It offers a suite of tools that cater to the entire API lifecycle, from creating API documentation to fostering internal API collaboration and governance. Built on the foundation of the widely popular Redoc API docs tool, ReDocly extends its functionality to help teams build, manage, and optimize their API ecosystems.

    License: MIT

    Repo: https://github.com/Redocly/redoc

    GitHub stars: 23k+

    Contributors: 200+

    Key features of ReDocly:

    • ReDoc (API reference tool): Automatically generates fast, SEO-ready API documentation from OpenAPI definitions. ReDoc’s responsive interface ensures usability with features like nested schemas, deep links, and auto-generated code samples.
    • Reunite (collaboration platform): Simplifies API collaboration by bringing stakeholders together on a single platform for design, review, and editing. Features like side-by-side visual reviews and a WYSIWYG editor support the API design and development process.
    • Revel (developer hub): Improves developer onboarding with personalized experiences and interactive content. Allows teams to create custom guides, landing pages, and integrated search, while tracking user engagement through rich analytics.
    • Reef (internal API platform): Breaks down API silos and manages internal APIs efficiently. Helps users discover and optimize internal APIs while using scorecards to track API performance.
    • Governance: Includes tools for building, nurturing, and managing the API ecosystem, ensuring that APIs are consistent, compliant, and discoverable across the organization.

    Source: ReDocly 

    4. Stoplight

    Stoplight is an API design platform that simplifies the API development lifecycle with a focus on design-first principles. By offering a modern and intuitive interface, it allows teams to design, document, and build APIs more efficiently. 

    License: Apache-2.0

    Repo: https://github.com/stoplightio/prism

    GitHub stars: 4k+

    Contributors: 80+

    Key features of Stoplight:

    • API design-first workflow: Optimizes API development by starting with design, enabling teams to create clear API specifications using OpenAPI standards (OAS) and providing developers with well-defined requirements.
    • Reusable models and components: Builds consistent and high-quality APIs by reusing models and components across the API portfolio. This “don’t repeat yourself” (D.R.Y.) approach ensures that APIs are efficient, scalable, and easier to maintain.
    • Collaboration and visibility: Helps ensure all stakeholders, from designers to developers, have visibility into the entire API lifecycle. 
    • API documentation: Generates thorough API documentation that is easy to read and understand. 
    • Integrated mock servers: Users can test APIs during the design phase. This helps developers and stakeholders validate functionality before implementation.

    Source: Stoplight

    5. DapperDox

    DapperDox is an open-source platform to enhance the presentation and usability of API documentation. It provides integration of OpenAPI specifications with GitHub Flavored Markdown documentation, allowing teams to create cohesive and interactive API guides. 

    License: GPL-3.0 

    Repo: https://github.com/DapperDox/dapperdox

    GitHub stars: ~400

    Contributors: <10

    Key features of DapperDox:

    • OpenAPI integration: Publishes OpenAPI Swagger specifications, making them more accessible and easier to navigate for developers and users alike.
    • Multiple API specifications: Documents multiple APIs as a unified suite of products, with built-in support for cross-referencing between specifications.
    • Markdown support: Allows developers to author full documentation in GitHub Flavored Markdown and overlay it onto their Swagger API specs. This enables them to write detailed guides and inject relevant content directly into the API documentation.
    • Built-in API explorer: Users can experiment with APIs directly within the documentation pages using the integrated API explorer. It allows developers to test endpoints, integrating with the organization’s authentication and API key models for real-time interaction.
    • Site integration: Can proxy the developer platform, enabling integration of API key generation and management within the documentation.

    Source: DapperDox 

    6. Postman

    Postman is an API platform that simplifies every stage of the API lifecycle, from design to testing, documentation, and deployment. It automatically generates API documentation for OpenAPI 2.0 and 3.0 definitions.

    Key features of Postman:

    • API repository: Centralized storage for all API-related artifacts, including specifications, documentation, test cases, and metrics, enabling collaboration across teams. Provides a unified place to store create, manage, and view API documentation.
    • Tools: Provides tools for API design, testing, mocking, documentation, and sharing, speeding up the API development process and improving discoverability.
    • Governance: Enables a “shift left” approach to API governance, enhancing collaboration between development and design teams and ensuring better-quality APIs throughout the lifecycle.
    • Workspaces: Offers four types of workspaces—personal, team, partner, and public—that help organize API projects and improve collaboration, whether internally or with external partners.
    • Integrations: Integrates with development tools and platforms, enabling API-first development practices and helping ensure consistent documentation.

    Source: Postman

    7. Document360

    Document360 is a platform to simplify the creation and management of API documentation. By centralizing API documentation, it enables teams to create clear, easy-to-understand API guides, test APIs, and simplify communication between developers.

    Key features of Document360:

    • Centralized API documentation: Provides a single platform to manage all API documentation, ensuring that teams can easily create, update, and maintain API guides in one place.
    • Interactive API guides: Simplifies the process of creating detailed API guides, making complex APIs more understandable for developers and end-users alike.
    • API testing: Offers built-in tools for testing APIs directly within the documentation, ensuring that developers can validate APIs and resolve issues without switching platforms.
    • Automated notifications: Automatically sends updates and notifications to keep developers informed about changes in API documentation.
    • Collaboration-friendly: Enables collaboration across teams by providing a shared platform for developers to work together on API documentation, ensuring consistency and accuracy across all docs.

    Source: Document360 

    8. SwaggerHub

    SwaggerHub is an API documentation tool to help teams create, manage, and collaborate on APIs. It supports multiple API standards, such as OpenAPI and AsyncAPI, enabling teams to accelerate the API design process while ensuring consistency and quality across projects. 

    Key features of SwaggerHub:

    • Interactive editor: Offers syntax auto-completion and real-time error feedback to simplify API design and ensure compliance with standards.
    • Standardization: Enforces consistent API design standards, helping teams maintain quality and style across different API projects.
    • Collaboration tools: Allows multiple team members to work on API files simultaneously, ensuring smoother workflows and reducing integration issues.
    • API auto-mocking: Automatically generates API mocks during design, allowing teams to test and validate APIs early in the development cycle.
    • Hosted documentation: Provides centralized, hosted API documentation for easy sharing and reference, ensuring that all stakeholders have access to the latest version.

    Source: SwaggerHub 

    9. Apidog

    Apidog is an API development platform built for API design-first development. It helps teams collaborate effectively and maintain a single source of truth for their APIs. With support for multiple protocols and an intuitive interface, Apidog combines the functionality of several API tools into one.

    Key features of Apidog:

    • API development toolkit: Allows developers to design and develop APIs using a visual editor that supports JSON and XML schema generation. 
    • Automated API testing: Creates automated test cases directly from API specifications, adding assertions visually and generating test scenarios with branching and iterations. Integrates with CI/CD pipelines to automate testing across the API lifecycle.
    • Online API documentation: Generates and publishes visually appealing API documentation with features like “try it out” functionality and example code. Users can customize domains, headers, and layouts.
    • Smart mock server: Automatically generates mock data based on field names and specifications without users writing scripts. Mocking features allow for customized responses based on request parameters.
    • Multi-protocol support: Handles HTTP, REST, GraphQL, SOAP, and WebSocket requests within a single platform, eliminating the need for switching between tools. 

    Source: Apidog 

    Conclusion 

    API documentation tools play a vital role in simplifying the process of creating, maintaining, and sharing API documentation. By automating documentation generation, supporting multiple API types, and offering features like search functionality, version control, and collaboration tools, these platforms ensure that developers and end-users can efficiently understand and use APIs.