doc-writer

Transform undocumented code into comprehensive, accurate documentation. doc-writer reads your source code, understands its behavior, and generates documentation in the format your project needs — from inline JSDoc comments to full OpenAPI 3.1 specifications.

What It Does

doc-writer produces documentation at every level of granularity:

• OpenAPI/Swagger specs: Generate complete OpenAPI 3.1 specs from Express, FastAPI, gin, or Axum route handlers
• JSDoc / TSDoc: Inline documentation for TypeScript/JavaScript functions, classes, and interfaces
• Rustdoc: /// doc comments for Rust functions, structs, traits, and modules
• Python docstrings: Google, NumPy, and Sphinx-style docstrings for Python functions and classes
• README generation: Project README with overview, installation, usage, API reference, configuration, and contributing sections
• Architecture diagrams: Mermaid.js diagrams for data flow, ER diagrams, service dependency graphs
• Changelog generation: CHANGELOG.md from conventional commit history
• Migration guides: Upgrade documentation comparing API versions

Installation

anvil skill install doc-writer

Usage

Generate OpenAPI Spec from Express Router

/doc-writer openapi ./src/routes/

Add JSDoc to a TypeScript File

/doc-writer jsdoc ./src/lib/crypto.ts

Generate README for Current Project

/doc-writer readme

Generate Architecture Diagram

/doc-writer diagram --type erd ./prisma/schema.prisma

Generate Changelog from Git History

/doc-writer changelog --since v1.0.0

Document a Python Module

/doc-writer docstring ./app/services/auth.py --style google

Generate Full API Reference Site

/doc-writer site --output ./docs/api

Supported Output Formats

Doc Type	Formats
API Spec	OpenAPI 3.1, Swagger 2.0, RAML, AsyncAPI
Inline	JSDoc, TSDoc, Rustdoc, Google/NumPy/Sphinx docstrings
Diagrams	Mermaid.js, PlantUML, Graphviz DOT
Site	HTML (static), MkDocs, Docusaurus, VitePress

Configuration Options

Option	Description	Default
--format	Output format	auto-detect
--output	Output path	./docs
--style	Docstring style (google, numpy, sphinx)	google
--overwrite	Overwrite existing docs	false
--dry-run	Preview without writing	false
--include-private	Document private/internal members	false

Requirements

• Source directory or specific files to document
• For OpenAPI generation: Express/Fastify/gin/Axum/FastAPI route handlers