Code-first OpenAPI specification generator for frameworks that don't hold your hand.

api2spec analyzes your API code and generates OpenAPI 3.1 specifications automatically. It uses tree-sitter for static analysis - no runtime dependencies needed, perfect for CI/CD pipelines.

┌─────────────────┐     ┌──────────────────┐     ┌─────────────────┐
│  Your Code      │────▶│    api2spec      │────▶│  openapi.yaml   │
│  (Any Framework)│     │  Parse + Infer   │     │  (auto-synced)  │
└─────────────────┘     └──────────────────┘     └────────┬────────┘
                                                          │
                                                          ▼
                                                 ┌─────────────────┐
                                                 │  Scalar/Redoc   │
                                                 │  (your docs)    │
                                                 └─────────────────┘

brew install api2spec/tap/api2spec

go install github.com/api2spec/api2spec@latest

git clone https://github.com/api2spec/api2spec
cd api2spec
go build ./cmd/api2spec

# Initialize config (auto-detects framework)
api2spec init

# Generate OpenAPI spec
api2spec generate

# Watch for changes
api2spec watch

# Validate spec matches code (for CI)
api2spec check --ci

# Show differences
api2spec diff

36 frameworks across 15 languages - with more being added regularly.

api2spec looks for configuration in this order:

1. api2spec.yaml
2. api2spec.json
3. .api2spec.yaml
4. .api2spec.json

Example configuration:

framework: chi  # or auto-detect

source:
  paths:
    - ./internal/api
    - ./cmd/server
  include:
    - "**/*.go"
  exclude:
    - "**/*_test.go"
    - "**/mocks/**"

output:
  path: openapi.yaml
  format: yaml

openapi:
  info:
    title: My API
    version: 1.0.0
  servers:
    - url: http://localhost:8080
      description: Development

- name: Check API spec
  run: |
    go install github.com/api2spec/api2spec@latest
    api2spec check --ci

#!/bin/sh
api2spec check --strict || exit 1

api2spec uses tree-sitter for static source code analysis instead of runtime reflection:

This makes api2spec ideal for CI pipelines where you don't want to install framework dependencies just to generate documentation.

# Run tests
go test ./...

# Build
go build ./cmd/api2spec

# Run
./api2spec --help

FSL-1.1-MIT (Functional Source License)

You may use api2spec freely in your projects. The only restriction is offering it as a hosted/managed service. After 2 years from each release, that version converts to MIT.

See LICENSE.md for details.