# Docker Hub

Docker Hub is a cloud-based registry service for building, sharing, and managing containerized applications. It provides a central repository for Docker images, allowing users to store, distribute, and download pre-built images or create their own. Developers use Docker Hub to streamline application deployment by packaging dependencies and code into portable containers.

## Level 1 / Basic Accessibility

- 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): PASS  
- Includes Schema.org JSON-LD structured data: PASS  
- Does not block automated access with CAPTCHAs on public content: FAIL  
- 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

- Has a robots.txt that allows legitimate bot access: PASS  
- Provides an XML sitemap: PASS  
- 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: PASS  
- Primary content is text-based (not locked in images/videos/PDFs): PASS

## Level 3 / Structured Interaction

- Provides a structured REST or GraphQL API: FAIL  
- API returns JSON responses with consistent schema: PASS  
- API supports search and filtering parameters: PASS  
- 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

- Provides an MCP (Model Context Protocol) server: PASS  
- Supports WebMCP for browser-based agent interaction: FAIL  
- API supports write operations (POST/PUT/PATCH/DELETE), not just reads: PASS  
- 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

- 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: PASS  
- Can proactively notify agents of relevant changes: FAIL  
- Supports cross-service handoff between agents: FAIL