Facet UCP Shopping

complete_checkout

Complete a checkout you created and place the order by submitting the buyer-signed payment credential. This is the MONEY-MOVING leg: funds capture on-chain to the merchant's pay_to (x402) or into escrow (Boson). The amount is re-derived server-side from the reservation, never your request, and the buyer's signature is verified before any capture. A per-buyer refusal (FORBIDDEN, cap-exceeded, FULFILLMENT_REQUIRED) returns as an error result; a missing or invalid identity is a real 401. REQUIRES IDENTITY plus a signed Idempotency-Key on a signature-required Terminal.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`payment`	Yes	The payment container `{ instruments: [{ credential: { type, ... } }] }`, where credential.type is `x402_authorization` or `boson_commit_authorization`. Sign the seller-signed offer LOCALLY with your own wallet; Facet never holds your key.
`checkout_id`	Yes	The checkout id from create_checkout.

TDQS

A4.6/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description fully discloses the high-stakes behaviors: funds capture on-chain or into escrow, server-side amount re-derivation, signature verification, specific error mappings (per-buyer refusal vs. real 401), and required identity/signature conditions. This is exemplary transparency for a money-moving operation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is dense but every sentence delivers critical information: purpose, money-moving nature, verification, error semantics, and prerequisites. It is front-loaded with the core action. Slightly long, but for a high-risk irreversible operation, the length is justified.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

This tool is complex (money movement, identity, signatures, two payment paths) with no output schema and no annotations. The description covers behavioral outcomes, error cases, and prerequisites thoroughly. It provides enough context for an agent to invoke it correctly and anticipate failure modes.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% for both parameters, so the baseline is 3. The description adds meaningful nuance, especially for the payment parameter: it explains that the credential must be signed locally and that Facet never holds the key, which is critical security context beyond the schema's type definition.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's function: completing a checkout and placing an order. It explicitly identifies this as the 'MONEY-MOVING leg' and contrasts with sibling tools like cancel_checkout and update_checkout, making its unique role unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives strong contextual cues: it is used on a checkout you created, after obtaining a buyer-signed payment credential, and requires identity and a signed Idempotency-Key. It does not explicitly name alternative tools or say 'use this instead of X', but the prerequisites and the money-moving emphasis implicitly distinguish it from related checkout operations.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All Facet UCP Shopping tools Inspect

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TDQS

A3.6/5.0

Disambiguation3/5

Most tools map to a distinct lifecycle step, and the detailed descriptions separate discovery, cart, checkout, payment, order, and wishlist concerns well. However, get_product and lookup_catalog are largely the same lookup by identifier, discover_products and search_catalog overlap across scope, and update_checkout is actually a read-only no-op.

Naming Consistency4/5

The set overwhelmingly follows a verb_noun pattern: create_cart, get_checkout, cancel_checkout, complete_checkout, search_catalog. Minor deviations are the wishlist_* resource-first subgroup and the misleading update_checkout, which does not perform an update.

Tool Count3/5

At 23 tools, this sits at the heavy end of the range, though the broad commerce lifecycle does justify substantial surface area. The count is inflated by redundant product lookup tools and a no-op update_checkout, so a more trimmed set in the low-to-mid teens would be healthier.

Completeness4/5

The server covers the full shopper lifecycle well: discovery, product lookup, cart, checkout, payment, order placement, order read, refunds, and wishlist. Gaps are minor and workable, such as update_checkout not actually supporting updates and no explicit order-cancellation path once a checkout is complete.

Resources

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