OpenAPI Tools and Projects
OpenAPI is a standard for describing HTTP APIs in a machine-readable format, commonly using JSON or YAML. A shared definition records endpoints, request and response formats, authentication, and other interface details. This helps teams document APIs consistently, validate changes, generate client libraries, and connect services without relying on scattered or ambiguous explanations.
Open source tools in this area include definition editors and validators, documentation and code generators, testing utilities, and adapters that expose APIs to other systems. When choosing one, consider its support for relevant OpenAPI versions, maintenance activity, license, language and runtime requirements, and fit with your development workflow. These tools are useful to API designers, backend and frontend developers, and teams integrating services.
5 repositories · updated March 10, 2026
Fern: Generate Type-Safe SDKs and API Documentation from OpenAPI
Fern is a powerful platform that streamlines API development by transforming your API definitions into production-ready SDKs and comprehensive documentation. It supports various API specifications, including OpenAPI, and offers multi-language SDKs, interactive developer documentation, and AI-powered search. This tool significantly enhances the developer experience by automating crucial parts of the API lifecycle.
mcpo: A Simple, Secure MCP-to-OpenAPI Proxy Server
mcpo is a dead-simple proxy server that transforms any Model Context Protocol (MCP) tool into an OpenAPI-compatible HTTP server. This allows seamless integration of MCP tools with LLM agents and applications that expect standard RESTful OpenAPI interfaces, eliminating the need for custom protocols or complex glue code. It enhances security, stability, and interoperability for AI tools, making them instantly usable with modern web standards.
oRPC: Typesafe APIs Made Simple with RPC and OpenAPI
oRPC combines RPC and OpenAPI to simplify building end-to-end type-safe APIs. It offers robust features like first-class OpenAPI support, contract-first development, and seamless integration with popular frameworks. This powerful tool ensures type safety from client to server while adhering to industry standards.
openapi-servers: Reference Implementations for LLM Tool Integration
The openapi-servers repository provides reference implementations for OpenAPI Tool Servers, simplifying the integration of external tools and data sources into LLM agents and workflows. By leveraging the OpenAPI specification, it ensures secure and easy communication without proprietary protocols. This project aims to accelerate the development of powerful AI applications by offering battle-tested, standard-compliant server examples.
FastAPI: High-Performance Python Web Framework for Building APIs
FastAPI is a modern, high-performance Python web framework designed for building APIs quickly and efficiently. It leverages standard Python type hints to provide automatic data validation, serialization, and interactive API documentation, making development intuitive and robust. This framework is ideal for production-ready applications, offering speed comparable to NodeJS and Go.