UCP Gateway

shopping cart update

shopping_cart_update

Replace a merchant cart with the full desired cart state.

Input Schema

TableJSON Schema

Name	Required	Description
`cart`	Yes	Full replacement cart state. Include the complete desired line_items list, not a patch.
`cart_id`	Yes	Provider cart ID returned by cart tools.
`agent_id`	Yes	Registered UCP Gateway UUID returned by register_ucp_profile; required for every Shopping tool.
`merchant_domain`	Yes	Merchant host such as 'outboundpower.com' or 'example.myshopify.com'. Do not include a URL scheme, localhost, private IP, file URL, or ftp URL.
`client_action_id`	No	Optional UUID generated once for an explicit buyer/operator-confirmed cart or checkout mutation. Reuse only when retrying the same confirmed action.

Output Schema

TableJSON Schema

Name	Required	Description
`ok`	Yes	True for successful tool execution; false for structured tool errors.
`raw`	No	Redacted raw provider or registry payload for debugging. Shape may vary by upstream endpoint.
`cart`	No	Safe provider cart summary including id, status, continue_url, totals, line_items, and messages when provided.
`error`	No	Structured tool error.
`message`	Yes	Human-readable result summary or recovery message.
`next_step`	Yes	Recommended next step. Suggestions are non-binding and never authorize payment or state-changing actions.
`merchant_domain`	No	Resolved merchant domain.
`commerce_session_id`	No	Internal gateway commerce session UUID when one was created.

Schema Changelog

Changes observed during successful MCP inspections.

First observedJun 5, 2026

TDQS

A3.5/5.0

Behavior3/5

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

Annotations provide readOnlyHint=false and destructiveHint=false. The description says 'Replace,' implying mutation, but does not add behavioral details beyond annotations (e.g., permissions, reversibility). No contradiction found.

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

Conciseness5/5

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

The description is a single concise sentence, front-loaded with the key action, and contains no unnecessary words.

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

Completeness3/5

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

Given the tool's complexity (5 params, nested objects) and existing output schema, the description is minimal. It covers the core functionality but omits higher-level context like error handling or prerequisites.

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

Parameters3/5

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

Schema coverage is 100%, so the baseline is 3. The description does not add additional meaning beyond the schema; it only restates the replacement intent.

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 'Replace a merchant cart with the full desired cart state,' specifying a concrete verb and resource, and distinguishes from siblings like shopping_cart_create and shopping_cart_cancel.

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

Usage Guidelines2/5

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

The description provides no explicit guidance on when to use this tool versus alternatives (e.g., shopping_cart_create or shopping_checkout_update). It lacks when-to-use or when-not-to-use instructions.

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

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