# AutoChemSDS - Free & Open Chemical Safety Database (Agent-Ready)

> AutoChemSDS provides free, unauthenticated, programmatic access to chemical Safety Data Sheets (SDS), GHS classifications, CAS registry mapping, and acute toxicity data. Designed for autonomous AI agents, researchers, and global open chemical intelligence.

## Base URL
- Production: `https://autochemsds.com`
- API Docs (OpenAPI): `https://autochemsds.com/docs`
- OpenAPI JSON: `https://autochemsds.com/openapi.json`

## Agent Best Practices
1. **Zero Auth / Free**: No API key, token, or account registration required.
2. **Rate limit**: Each IP may make 35 requests to `/api/v1/*` per day (UTC+8). Exceeding the limit blocks the IP (1 day, then 3 days, then permanently) until support is contacted. Check the `X-RateLimit-Remaining` response header and cache results instead of re-requesting.
3. **Direct Markdown Endpoints**: AI models should preferably request `/api/v1/chemical/{cas}/markdown` to receive concise, pre-formatted Markdown directly within context windows with minimal token overhead.
4. **Identifier Flexibility**: You can pass either a standard CAS number (e.g. `64-17-5`) or chemical names in English/Chinese (e.g. `ethanol`, `乙醇`).

## Key Endpoints

- `GET /api/v1/chemical/{identifier}?lang=zh|en`
  Retrieve complete structured JSON data including GHS hazard statements, physical characteristics, molecular formula, first aid, and acute toxicity test records.

- `GET /api/v1/chemical/{identifier}/markdown?lang=zh|en`
  Retrieve human and LLM readable Safety Data Sheet in pure Markdown.

- `GET /llms.txt`
  This document.