Serve at least 500 characters of meaningful homepage content in raw HTML. Add a clear H1, keep deeper heading levels sequential, and remove excessive non-content markup.

Keep the correct HTTP 404 status. The remaining requirement is a Markdown error body when agents request Accept: text/markdown. Include at least 20 characters explaining the error and a link to your docs, sitemap, or llms.txt. Verify with curl -sS -L -i -H 'Accept: text/markdown' https://yourdomain.com/some-path-that-does-not-exist. Check both the final 404 status and the Markdown body with Content-Type: text/markdown. Checking the status alone does not verify the missing requirement.

Make sure your own domain ranks in the top results when people search your brand together with your main product (for example "Acme payments API"). If it does not, your brand may be too generic, conflict with a more established term, or not yet indexed. Strengthen it by describing your main product clearly in your homepage title and headings, earning press mentions that link to your domain, and avoiding redirect chains that mask your main domain in search results.

Tell agents when to reach for you: add a 'when to use this' section to your llms.txt (or a dedicated agent-instructions file) that names your best-fit use cases and how an agent should call you. Be specific about the jobs you are right for - generic marketing copy does not read as guidance.

Keep authentication enabled. Verify tool listing with an authorized MCP client. This unauthenticated scan cannot establish whether protected tools are missing or unusable.

Return standard rate-limit headers on your API responses (the RFC RateLimit headers, plus Retry-After on a 429) so agents can self-throttle in real time, and document the conventions alongside your API.

Document your error responses in your OpenAPI spec: give 4xx and 5xx responses a typed error schema (or use RFC 9457 application/problem+json). A consistent error object with a machine-readable code and a human-readable message lets agents handle failures without guessing.

Declare a versioning policy agents can rely on: version your API (in the URL path or a version header) and publish how you signal deprecation (a Sunset/Deprecation header or a documented timeline). Agents avoid integrating against a surface that can change without warning.

Make your API spec self-describing: a unique operationId and a description on every operation, typed parameters, and response schemas. For GraphQL, a fully typed schema with a documented cost or rate limit reads best.

Ensure API endpoints have unique operation IDs, typed schemas, and descriptions compatible with LLM function-calling formats.

Establish a Wikipedia article and a Wikidata entity for your brand, with the domain set as the official website (Wikidata property P856) and a corresponding external link on Wikipedia. Wikipedia is the largest single source of citations in ChatGPT and a primary input to Knowledge Graphs across Google, Bing, and LLM training data. Earn third-party press coverage first to satisfy notability, then draft the article with cited references rather than self-promotion.

Give your MCP server-card (at /.well-known/mcp/server-card.json) a display name, an icon or logo, and a description - all three together are what reads as a complete, branded listing agents can present.

Expand your JSON-LD beyond Organization/WebSite. Add FAQPage for common questions, Service or Product for offerings, AggregateRating or Review for social proof, and BreadcrumbList for navigation context.

Make every link your llms.txt declares resolve to real content. Verify each one with curl -L <url> - you should see the linked document, not your homepage. If your app returns the homepage shell for unknown paths (common with single-page apps), a 200 status is not proof: check the body. Fix or remove any dead link; agents that follow the index treat a broken link as a dead end.

Publish an API catalog at /.well-known/api-catalog per RFC 9727. Serve it with Content-Type: application/linkset+json;profile="https://www.rfc-editor.org/info/rfc9727" and include a 'linkset' array with item entries pointing to your OpenAPI specs and service descriptions.

Structure /auth.md as the WorkOS spec prescribes: sections for Discover, Pick a method, Register, Claim, Exchange, Use the access_token, Errors, and Revocation, with spec anchor keywords (agent_auth, identity_endpoint, identity_assertion, service_auth, id-jag, WWW-Authenticate). Reference https://github.com/workos/auth.md.

Make your published auth-discovery chain traversable end to end: an agent starting at /auth.md (or your protected-resource metadata) should be able to follow the links to your authorization-server metadata and registration endpoint without hitting a dead link. Test the whole path, not just each file in isolation.

Publish RFC 9728 protected-resource metadata at /.well-known/oauth-protected-resource on your resource server (the host that actually serves the API, e.g. api.<apex>) with resource and authorization_servers. Publish RFC 8414 authorization-server metadata at /.well-known/oauth-authorization-server on the AS origin, and include the WorkOS auth.md agent_auth block with identity_endpoint, identity_types_supported drawn from the spec enum (anonymous, identity_assertion, service_auth - the assertion variant, the ID-JAG URN urn:ietf:params:oauth:token-type:id-jag, belongs inside identity_assertion.assertion_types_supported, not at the top level), and the identity_assertion.assertion_types_supported block when you advertise that type, so agents can check their assertion shape is accepted before minting. Cross-link by listing the AS origin in PRM authorization_servers, and point agent_auth.skill back at your published /auth.md. Spec: https://github.com/workos/auth.md.

Expose in-page tools through WebMCP, a proposed web standard for browser agents. Register tools with document.modelContext.registerTool() and use navigator.modelContext only as a trailing compatibility fallback. Declarative forms with toolname and tooldescription provide server-rendered evidence, but remain a preview and should not be your only tool surface. Chrome's origin trial covers versions 149-156, with shipping currently targeted for 157. ChatGPT can discover and call WebMCP site tools in the desktop app's built-in browser when the feature is available.

For long-running operations, return 202 Accepted and point agents at where to poll for the result (a status/location reference plus a job identifier in the body), documented in your OpenAPI spec, so work that does not finish in one request is still followable.