---
title: "UCP Checkout Payload Lint"
method: POST
path: "/v1/tools/lint_ucp_checkout_payload"
tags: ["TODO_TAGS_REVIEW", "TODO_AP2_EXPORT_REVIEW"]
---

# UCP Checkout Payload Lint

`POST /v1/tools/lint_ucp_checkout_payload`

## Request

- Base URL: `https://ainumbers.co`
- URL: `https://ainumbers.co/v1/tools/lint_ucp_checkout_payload`
- Auth: none declared

Deterministic, verify-only structural lint of a caller-supplied Universal Commerce Protocol (UCP; Google + Shopify, announced NRF 2026-01-11, Apache-2.0 spec on GitHub) checkout resource against the schema pinned at tag v2026-04-08 of github.com/Universal-Commerce-Protocol/ucp. Checks the resource-level required[] field set, the status enum, ISO 4217 currency form, integer minor-unit amounts, and the exactly-one-subtotal / exactly-one-total cardinality rule on totals[]. Verdict CONFORMANT | NONCONFORMANT | UNKNOWN_VERSION: a payload declaring a UCP version outside the pinned allowlist is capped at UNKNOWN_VERSION regardless of otherwise-clean structure, never upgraded to CONFORMANT for a version this kernel has no pinned rules for. Never contacts a UCP or ACP endpoint and never fetches a live spec version -- the caller supplies the payload. UCP composes with AP2 rather than competing with it; part of the agentic-commerce-convergence chain alongside art-12 (ACP checkout conformance) and art-01 (AP2 mandate-chain validator).

**Tool URL:** https://ainumbers.co/chaingraph/art-564-ucp-checkout-payload-lint.html

## Request body

- object
  - `payload` unknown, required

## Response `200`

Successful tool execution result

- object
  - `error_count` integer
  - `finding_count` integer
  - `findings` unknown[]
    - unknown
  - `note` string
  - `rationale` string[]
  - `ucp_spec_pinned_tag` string
  - `ucp_spec_source` string
  - `ucp_version_declared` string
  - `verdict` string
  - `warning_count` integer

---

[API](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite.md) · [All operations](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite/llms.txt) · [OpenAPI document](https://skmtc.dev/ainumbers/apis/ainumbers-co-fintech-intelligence-suite/revisions/b462e4f5bb28?raw)