agents.txt + agents.json

An open-standard machine-readable site index for autonomous AI agents. Inspired by robots.txt (crawler discovery) and llms.txt (LLM context); agent-first: tells agents which paid endpoints exist, how they're priced, and how to authenticate.

Why

Agents discover services the same way humans do — by GET-ing predictable URLs. /agents.txt at the root of any service is a single fetch that surfaces every machine endpoint, every pricing constant, and every discovery manifest the service publishes. No more scraping marketing pages.

Two formats, one source of truth

• /agents.txt — line-oriented Key: value for grep-friendly tooling and LLM context windows.
• /agents.json — same data, structured, schema-validated.

Required keys

• Site, Vendor, Vendor-URL
• Pricing-Model, Free-Tier, Signup-Required
• At least one of: Refuel, OpenAPI, MCP-Endpoint, AI-Plugin
• Contact

Live example

x711's /agents.txt · x711's /agents.json

Adoption

If you publish /agents.txt on your service, ping facts@x711.io and we'll add you to awesome-x711 + the cross-vendor agent index.

License

The format is CC0. Use it freely.