jsonplaceholder.typicode.com.

level 1: basic accessibility

JSONPlaceholder provides a free, fake REST API for testing and prototyping. It offers common endpoints like posts, comments, and todos, returning JSON data for each request. You can use it by making standard HTTP requests (GET, POST, PUT, DELETE) to its endpoints, allowing you to simulate backend interactions without needing a real server.

LEVEL 1 / BASIC ACCESSIBILITY — 4/6

Uses semantic HTML elements (header, nav, main, article, section, footer) instead of just divs PASS

Has proper meta tags (title, description, og:tags, twitter:card) FAIL

Includes Schema.org JSON-LD structured data FAIL

Does not block automated access with CAPTCHAs on public content PASS

Content is server-side rendered (visible in HTML source, not just JS-rendered) PASS

Uses clean, readable URLs (no excessive query params or hash fragments) PASS

LEVEL 2 / DISCOVERABILITY — 2/6

Has a robots.txt that allows legitimate bot access PASS

Provides an XML sitemap FAIL

Has a /llms.txt file describing the site for LLMs FAIL

Publishes an OpenAPI/Swagger specification for its API FAIL

Has comprehensive, machine-readable documentation FAIL

Primary content is text-based (not locked in images/videos/PDFs) PASS

LEVEL 3 / STRUCTURED INTERACTION — 2/6

Provides a structured REST or GraphQL API PASS

API returns JSON responses with consistent schema PASS

API supports search and filtering parameters FAIL

Has an A2A agent card at /.well-known/agent.json FAIL

Rate limits are documented and return proper 429 responses with Retry-After FAIL

API returns structured error responses with error codes and messages FAIL

LEVEL 4 / AGENT INTEGRATION — 0/6

Provides an MCP (Model Context Protocol) server FAIL

Supports WebMCP for browser-based agent interaction FAIL

API supports write operations (POST/PUT/PATCH/DELETE), not just reads FAIL

Supports agent-friendly authentication (API keys, OAuth client credentials) FAIL

Supports webhooks for event notifications FAIL

Write operations support idempotency keys FAIL

LEVEL 5 / AUTONOMOUS OPERATION — 1/6

Supports event streaming (SSE, WebSockets) for real-time updates PASS

Supports agent-to-agent capability negotiation FAIL

Has a subscription/management API for agents FAIL

Supports multi-step workflow orchestration FAIL

Can proactively notify agents of relevant changes FAIL

Supports cross-service handoff between agents FAIL