Top OPENAPI GitHub Repositories & Tools (2026)

Turn any REST, SOAP, GraphQL or SQL API into MCP tools for Claude & ChatGPT. Self-hosted. 258 connectors: ERP, e-commerce, SAP.

FastAPI framework, high performance, easy to learn, fast to code, ready for production

A sandbox for the third-party APIs you depend on. Built from the provider's spec, it fails on purpose, and it replays the exact failure production hit.

Detect breaking changes between OpenAPI 3.0/3.1 specs. Explainable Web UI, CLI and CI gate; local-first and deterministic, with optional AI summaries.

Typesafe APIs Made Simple 🪄

A Burp Suite extension that exposes the full Montoya API as a local REST API, with Swagger UI

Every API has a secret identity. This finds it, absorbs every feature from every competing tool, then builds the GOAT CLI — designed for AI agents first, with SQLite sync, offline search, and compound insight commands.

Input OpenAPI. Output SDKs and Docs.

OpenAPI Generator allows generation of API client libraries (SDK generation), server stubs, documentation and configuration automatically given an OpenAPI Spec (v2, v3)

gRPC to JSON proxy generator following the gRPC HTTP spec

Examples and server integrations for generating the Swagger API Specification, which enables easy access to your REST API

Super-fast/easy runtime validators and serializers via transformation

Open-source auth gateway connecting 1500+ SaaS providers to AI agents through SDK, CLI, MCP, HTTP, and OpenAPI.

OpenAPI based HTTP Client code generator

A fast, lightweight and more productive microservices framework

Next generation noIM application in your own workspace, not only another Slack/Discord/Rocket.chat

Self-Hosted API Management for Builders

The open source, cloud native tool for API Mocking and Testing. Microcks is a Cloud Native Computing Foundation incubating project 🚀

Generate Swift client and server code from an OpenAPI document.

Simulate API failures, throttling, and chaos — all from your command line.