Glossary — the pages LLMs cite most

Descriptor at /.well-known/agent-card.json for agent-to-agent discovery (identity, endpoints, skills, security). MUST if you expose an A2A surface.

Operational readiness to be agent-first. The HOW: implementing the AR-* requirements that apply to your surface (MUST/SHOULD/MAY per AgentReady v1.0.0).

Packaged SKILL.md files (YAML frontmatter + markdown) exposing discrete site capabilities. Index at /.well-known/agent-skills/. MAY.

Design paradigm: building the web so an agent can find, understand and use it end-to-end. The strategic WHAT.

Protocols for an agent to pay or checkout on behalf of the user: x402/MPP (402 Payment Required), ACP (OpenAI+Stripe) and UCP (Google+Shopify). MAY, one suffices for conformance.

Linkset at /.well-known/api-catalog listing public APIs and pointing to OpenAPI/AsyncAPI descriptors. MAY.

MUST directive in robots.txt (Content-Signal: ai-train=no, search=yes, ai-input=yes) separating training, search and RAG input permissions.

Federated discovery via DNS with _index._agents, _a2a._agents, _mcp._agents labels and DNSSEC verification. _index is the entry point.

Optimization to be cited by generative engines. Not SEO rebranded: rewards self-contained, verifiable content.

schema.org structured data embedded as <script type='application/ld+json'> so models read entities without running JS. SHOULD.

HTTP Link header with rel=sitemap, describedby, api-catalog or alternate to discover resources without parsing HTML.

Extended version of llms.txt: full documentation as a single ingestible file fitting the context window. MAY. Only makes sense alongside llms.txt.

Markdown index at site root summarizing the product and linking what agents should read first. SHOULD per AgentReady, not MUST. Useful for devtool docs, irrelevant for general SEO (Google: not used, fetch ≈0.12%).

Accept: text/markdown negotiation → rewrite to /markdown/[...path] serving clean, token-efficient markdown. MAY, emerging.

Open JSON-RPC protocol for exposing tools, resources and prompts to agents over Streamable HTTP or stdio. MUST if you expose tools to agents.

Layer to make any site conversational: schemamap.json referenced in robots.txt (Schemamap:) + /ask endpoint returning schema.org. MAY, emerging.

Machine-readable HTTP API description (paths, params, schemas, errors) agents use for function calling. MUST if you expose an API.

Centralized URL index so agents can list the site without crawling page by page. SHOULD for any public, indexable site.

HTTP Message Signatures to verify a request comes from an identified agent, with keys at /.well-known/http-message-signatures-directory. SHOULD, emerging.