ucp_checkout_set_fulfillment

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

No annotations are provided, so the description carries full burden. It discloses the key behavioral trait: 'Automatically selects the first available shipping address and delivery option,' informing the agent of this autonomous action.

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

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

The description is concise, front-loading the purpose and usage guidance. It includes structured Args and Returns sections, making it easy to scan. A slight reduction in verbosity could be possible, but overall it's efficient.

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

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

Given the simple 2-parameter schema and presence of an output schema, the description adequately covers purpose, when to call, behavioral details, and return fields. It could mention error conditions but is sufficiently complete for this tool.

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

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

Schema description coverage is 0%, but the description only lists the parameter names without adding meaning. The parameter names (merchant_url, checkout_id) are self-explanatory, but the description fails to provide additional context or constraints.

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

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

The description clearly states the tool's purpose: 'Set up shipping/fulfillment for a checkout.' It also explains automatic selection of shipping address and delivery option, distinguishing it from sibling tools like ucp_checkout_complete or ucp_checkout_create.

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

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

The description includes explicit usage guidance: 'Must be called before completing checkout if the merchant requires fulfillment.' This tells when to use it, though it does not mention when not to use or alternatives.

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