ucpplayground.com
verified_user Multi-version UCP compliance, backward compatibility & transport audit
schedule Last scanned 5/4/2026
Conformance
63%Capability
100%Coverage
24%Backward Compat
0%Negative
41%Transport
100%Latency
99%Audit Details
Cache-Control max-age is within recommended bounds
Cache-Control "no-cache, private" disables caching — agents will re-fetch on every request
Profile response advertises cache headers
Completed in 483ms
Profile declares at least the checkout capability
Completed in 224ms
Capability version strings are valid ISO dates
Completed in 192ms
Profile response Content-Type is application/json
Completed in 231ms
Discovery endpoint exposes CORS headers
Discovery response is missing Access-Control-Allow-Origin header
Profile is served over HTTPS
Completed in 314ms
Two consecutive profile fetches return identical bodies
Completed in 357ms
Signing JWKs use only allowed kty/crv values
Profile declares no signing_keys array — the field is optional per the UCP spec, but agents cannot verify signed payloads from this merchant
No duplicate capability entries (same name + version)
Completed in 195ms
OpenAPI servers[] URL is reachable
Profile has no loadable service-level OpenAPI document
Business profile has a valid structure
Completed in 196ms
Merchant responses are signed with the published signing_keys
Profile declares no signing_keys; nothing to verify against. DISC-0002 tracks absence separately.
robots.txt allows AI agents to read the UCP profile
5 of 5 AI agents are disallowed from /.well-known/ucp
All declared schema URLs use HTTPS
Completed in 195ms
Signing keys are importable via Web Crypto
Profile declares no signing_keys array — the field is optional per the UCP spec, but agents cannot verify signed payloads from this merchant
Profile advertises well-formed signing keys
Profile declares no signing_keys array — the field is optional per the UCP spec, but agents cannot verify signed payloads from this merchant
Service binding transports are in the allowed set
Completed in 205ms
Profile declares a ucp.version string
Completed in 240ms
Profile ucp.version is one the grader recognizes
Completed in 197ms
Profile is served at the canonical .well-known/ucp path
Completed in 205ms
Declared capabilities match operations in the OpenAPI
No OpenAPI operations available to cross-check
Capability JSON Schemas declare a modern $schema draft
Profile declares no capability JSON Schemas
Capability-level JSON Schemas are well-formed
Profile declares zero capability-level schemas
OpenAPI components.schemas has no orphans
Profile has no loadable service-level OpenAPI document
Service-level OpenAPI document is valid OpenAPI 3.x
No service-level OpenAPI schema was loaded
Every OpenAPI operation declares a 2xx JSON response schema
Profile has no loadable service-level OpenAPI document
Every $ref referenced schema document is reachable
Profile declares no loadable schema documents
All declared schema URLs return 200
1 of 1 schema URLs failed to load: [service] https://ucpplayground.com/ucp-merchant/openapi.json → http_404
Cancel session response matches the OpenAPI schema
Could not create session: 201
Create session response matches the OpenAPI schema
Schema unavailable: no_openapi
Discovery profile matches the published JSON Schema
ucp.payment_handlers is missing or not an object
Get session response matches the OpenAPI schema
Could not create session: 201
Update session response matches the OpenAPI schema
Could not create session: 201
Canceling a session twice with the same idempotency key is idempotent
First cancel returned status=404
Cancel a checkout session
cancelSession returned 404
Create checkout session with defaults
Checkout session failed schema validation
Repeated createSession with same idempotency key returns same session
Completed in 448ms
Create session then set shipping address
setShippingAddress returned 422
Retrieve a checkout session by id
getSession returned 404
Reusing an Idempotency-Key with a different body must be rejected
Server accepted a second create with the same idempotency key but a different currency (USD → EUR). Per the spec, the second call must be rejected.
update_checkout is idempotent on replay and rejects conflicting replays
First update returned status=422
Select a shipping method on a checkout session
setShippingAddress returned 422
Catalog capability advertised for product lookup
Profile does not declare dev.ucp.shopping.catalog.lookup
Catalog capability is declared
Profile does not declare dev.ucp.shopping.catalog.search
Checkout capability is declared and reachable
Completed in 232ms
Fulfillment capability is declared
Profile does not declare dev.ucp.shopping.fulfillment