# UCP Checker

> The independent standard for agentic commerce validation — the system of record for protocol adoption, observed continuously since day zero. Check any domain for UCP support, find the verified stores that sell what you need, search their live catalogues, and get each store's own endpoint to buy from — all programmatically.

UCP Checker validates, observes and scores stores that implement the Universal Commerce Protocol (UCP). UCP is a machine-readable manifest at `/.well-known/ucp` that exposes commerce capabilities to AI agents. Everything here is read-only: UCP Checker resolves stores and measures them, and never creates carts, checks out or takes payment. Once an agent has chosen a store, it transacts with that store's own endpoint.

## Agent discovery (ARD)

UCP Checker is an Agentic Resource Discovery (ARD v0.91) discovery service for the verified UCP storefronts in its census — the commerce Agent Finder:

- Capability manifest: https://ucpchecker.com/.well-known/ard.json (also served at the predecessor path, https://ucpchecker.com/.well-known/ai-catalog.json)
- Search (POST, JSON `{"query":{"text":"..."}}`): https://ucpchecker.com/ard/search
- Facets (POST): https://ucpchecker.com/ard/explore · Browse (GET): https://ucpchecker.com/ard/agents
- MCP server card: https://ucpchecker.com/.well-known/mcp/server-card.json
- Agent skills: https://ucpchecker.com/.well-known/agent-skills/index.json (`ucp-checker`, `ucp-agent-ready`)
- CLI: `npx ucp-check <domain>` — https://www.npmjs.com/package/ucp-check (source: https://github.com/ucpchecker/ucp-check)

Every entry is a verified, publicly listed storefront, labelled with the evidence we hold (`transactable`, `catalogued`, `resolvable` or `declared`). Search ranks lexically: rarer query words count for more, and stores below a relevance floor are not returned, so an empty result means no strong match. A query reaches its first 50 results. `score` on search results is relevance only; the UCP score is in `metadata.ucpScore`. Errors carry the spec's `errorCode` and `message`. Full reference: https://ucpchecker.com/docs#post-ard-search

## MCP Server

UCP Checker exposes a read-only Model Context Protocol (MCP) server for AI agents:

- Endpoint: https://ucpchecker.com/mcp
- Transport: HTTP (Streamable HTTP)
- Authentication: none required; signed (RFC 9421) and token callers get higher rate limits
- Schema: https://ucpchecker.com/.well-known/mcp.json
- Configuration: https://ucpchecker.com/.well-known/mcp-config
- Listed on: the official MCP Registry (`com.ucpchecker/ucp-checker`) and Smithery (https://smithery.ai/servers/ucpchecker/ucp-checker)

### Tools

- `check-domain` — Is a domain agent-ready? Returns UCP status, manifest version, capabilities, latency and AI bot access policies, as observed.
- `list-stores` — List verified UCP storefronts across every platform, best-evidenced first; filterable by platform.
- `list-categories` — Store categories with counts, for the deeply audited subset of verified stores (a way to browse, not the whole index).
- `search-all` — Search products across the verified stores whose observed catalogue matches the query; returns results grouped by store. When nothing matches well enough it answers "No strong match" instead of searching unrelated stores.
- `search-catalog` — Search one store's live product catalogue; returns titles, prices, variants and images.
- `get-product-details` — Full declared detail for one product, including variant IDs.
- `search-policies` — A store's return, shipping, refund, privacy and terms policies.
- `discover-store` — Connect to a store's own MCP endpoint and list the tools it exposes.

### Resolution flow

1. `search-all` (or `list-stores`) — which verified stores match
2. `search-catalog` → `get-product-details` — find the product and its variant
3. `check-domain` and `search-policies` — confirm the store's observed state and its policies
4. `discover-store` — see what the store itself offers, then buy through the store's own endpoint

A store missing from the index, or returning `not_detected`, has not been observed by us — it is not barred to you.

## REST API

- `POST /api/v1/check` — Force a fresh UCP check on a domain
- `GET /api/v1/status/{domain}` — Latest observed status for a domain
- `GET /api/v1/score-model` and `GET /api/v1/checks` — The score model and the check catalogue
- `GET /api/v1/schema` — JSON Schema for the API
- CLI over the API: `npx ucp-check <domain>` — exit 0 verified · 1 not verified · 2 usage · 3 API unreachable; `--cached`, `--json`, `--quiet`
- Reference: https://ucpchecker.com/docs

## Discovery

- UCP manifest: https://ucpchecker.com/.well-known/ucp
- ARD manifest: https://ucpchecker.com/.well-known/ard.json
- MCP schema: https://ucpchecker.com/.well-known/mcp.json

## RSS Feeds

- Blog: https://ucpchecker.com/rss/blog.xml
- UCP Adoption & Stability Stats: https://ucpchecker.com/rss/stats.xml

## Links

- Website: https://ucpchecker.com
- API & MCP docs: https://ucpchecker.com/docs
- Directory: https://ucpchecker.com/directory
- Leaderboard: https://ucpchecker.com/leaderboard
- Stats: https://ucpchecker.com/stats
- Methodology: https://ucpchecker.com/methodology
- CLI (npm): https://www.npmjs.com/package/ucp-check
- Blog: https://ucpchecker.com/blog
- UCP Playground: https://ucpplayground.com