Standards Glossary
Reference guide for open AI agent and GEO standards. Each term includes implementation examples and a link to the official spec.
Discoverability
- ai-agent.json Universal AI agent manifest: /.well-known/ai-agent.json describing site capabilities for agents (Aiia spec, March 2026).
- Link headers (RFC 8288) HTTP Link headers for agent discovery: API catalog, docs, status, terms (RFC 8288 + RFC 9727).
- llms.txt A structured markdown file at the site root with instructions and navigation for LLM agents.
- robots.txt Instruction file for search and AI crawlers: what is allowed or disallowed to index (RFC 9309).
- Sitemap XML site map enabling search engines and AI bots to discover all pages without link crawling.
Content Accessibility
Bot Access Control
- AI Bot Rules Explicit allow rules for AI crawlers (GPTBot, ClaudeBot, PerplexityBot) in robots.txt.
- Content Signals Declaration of consent for AI training and search in robots.txt via the Content-Signal directive (contentsignals.org).
- Web Bot Auth Cryptographic identification of AI bots via HTTP Message Signatures (RFC 9421): the bot signs requests with an Ed25519 private key; the site verifies the signature via the public key published at .well-known/http-message-signatures-directory.
API / Auth / MCP
- A2A Agent Card Machine-readable AI agent descriptor at /.well-known/agent.json (Google A2A Protocol).
- Agent Skills Index of specific tasks an AI agent can perform — machine-readable capabilities registry.
- API Catalog (RFC 9727) Machine-readable registry of all site APIs at /.well-known/api-catalog (RFC 9727).
- auth.md Markdown file /auth.md (WorkOS open protocol) telling AI agents how to register with a service: flows, scopes, and endpoints.
- MCP Server Card Machine-readable MCP server discovery card at /.well-known/mcp/ — enables AI agents to discover and use your MCP endpoint.
- OAuth Discovery Automatic discovery of OAuth 2.0 endpoints via /.well-known/oauth-authorization-server (RFC 8414).
- OAuth Protected Resource (RFC 9728) Metadata document /.well-known/oauth-protected-resource telling AI agents where to obtain an access token.
- RateLimit Headers (draft-ietf-httpapi-ratelimit-headers) Standard HTTP headers for informing AI agents about request limits: RateLimit-Limit, RateLimit-Remaining.
- WebMCP MCP over HTTP: access to MCP server via standard web requests without local installation.
Commerce
- ACP — Agentic Commerce Protocol Agentic checkout protocol by OpenAI and Stripe: AI agents complete purchases via Shared Payment Tokens without exposing payment details.
- MPP — Machine Payments Protocol Machine-to-machine payment protocol for AI agents: standard for autonomous transactions between agents.
- UCP — Universal Commerce Protocol Universal commerce protocol for AI agents: standard for discovering and purchasing goods/services.
- x402 Payment Protocol HTTP 402 Payment Required for AI agents: machine-to-machine micropayment standard via stablecoins.
Concepts
- AEO — Answer Engine Optimization Optimizing content for direct citation by answer engines: answer-first sentences, question-answer structure, machine-readable markup.
- Agent Readiness The degree to which a website is ready for AI agent interaction via open standards: from basic discoverability to full agentic access.
- GEO — Generative Engine Optimization Content optimization for AI search: how to appear in answers from ChatGPT, Perplexity, Gemini, and other AI assistants.