Top OPENAPI GitHub Repositories & Tools (2026)

Open-source, self-hosted MCP gateway: turn any REST/OpenAPI, SOAP, GraphQL, OData or SQL API into MCP tools for Claude, ChatGPT & Copilot. 265 connectors incl. SAP S/4HANA & Business One, ERP, e-commerce.

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

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

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.

Typesafe APIs Made Simple 🪄

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

Open-source OpenAPI mock server with cloud hosting and local modes for development, testing, and CI. Generates realistic API responses from specs with latency simulation, error injection, proxy fallback, and request validation. Validated against 2,200+ real-world OpenAPI specs.

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

Input OpenAPI. Output SDKs and Docs.

Swagger UI is a collection of HTML, JavaScript, and CSS assets that dynamically generate beautiful documentation from a Swagger-compliant API.

Light, flexible and extensible ASGI framework | Built to scale

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.

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

orval is able to generate client with appropriate type-signatures (TypeScript) from any valid OpenAPI v3 or Swagger v2 specification, either in yaml or json formats. 🍺

Generate Pydantic v2 models, dataclasses, TypedDict, and msgspec.Struct from OpenAPI, JSON Schema, GraphQL, Avro, Protobuf, and raw JSON/YAML/CSV.

OpenAPI based HTTP Client code generator

A fast, lightweight and more productive microservices framework

Catch API bugs before your users do

OpenAPI 3.0 and 3.1 and 3.2 (and Swagger v2) implementation for Go (parsing, converting, validation, and more)

Modern data layer for TypeScript apps - type-safe ORM, built-in access control, automatic query services