Does a valid profile mean agents can buy?

Not necessarily. ARC also checks whether a checkout link comes back.

How do I check if my UCP profile is valid?

Paste your store's address into ARC's free UCP validator. It fetches /.well-known/ucp and checks it against the published UCP schema and spec rules, then tells you what's wrong. Developers can call the same check by API or MCP, or add ARC's arc-check step to CI so a broken profile fails the build.

Use the validator

Open /developers/ucp-validator and paste the store address. ARC fetches /.well-known/ucp and checks the published schema and spec rules. No key and no login.

Common errors

The validator reports the rule that failed, on that profile. ARC does not publish a ranked list of error strings in this dataset, so this page does not invent one. Declared versus valid, from ARC saved checks, accessed 2026-10-13:

UCP declared: 1,896 of 4,318 (43.9%)Measured

UCP valid: 1,862 of 4,318 (43.1%)MeasuredThe gap is profiles ARC fetched that did not pass validation. It is not a list of error messages.

API, MCP and CI

The same check is GET /api/ucp/validate?url= and the MCP tool validate_ucp_profile on /api/ask. arc-check can fail a build when the profile breaks. Docs are on /developers/mcp.

What valid doesn't guarantee

A valid profile can still fail to return a product or a checkout link. Compare valid with transacts:

UCP transacts: 1,522 of 4,318 (35.2%)Measured

Frequently asked questions

How do I check if my UCP profile is valid?: Paste your store's address into ARC's free UCP validator. It fetches /.well-known/ucp and checks it against the published UCP schema and spec rules, then tells you what's wrong. Developers can call the same check by API or MCP, or add ARC's arc-check step to CI so a broken profile fails the build.
Is the validator free?: Yes, with no key or login.
Does a valid profile mean agents can buy?: Not necessarily. ARC also checks whether a checkout link comes back.

On ARC

Cite this: ARC, arcreport.ai, accessed 2026-10-13, CC-BY-4.0. Protocol figures: ARC saved checks, accessed 2026-10-13 (13 October 2026). Index browser figures: ARC open dataset snapshot 2026-10-12. Platform figures: ARC saved checks, accessed 2026-10-13.

Every figure is labelled Measured, Inferred or Not measured. Not measured is not zero. A missing result is not a mark against a store. ARC stops before payment.