four02_invoice_pay

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

With no annotations, the description carries the full burden and does so well: it discloses the dry-run default, that nothing is broadcast, that the server submits the USDC transfer when approved, and the environment prerequisite. This is exactly the safety-critical context a payment tool needs.

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?

Two sentences, front-loaded with the dry-run default and the approval gate, with no redundant filler. Every clause adds operational meaning.

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?

For a two-parameter payment tool with no output schema, the description covers the return contract ('returns the plan and client-side signing instructions'), the default mode, and the broadcast gate. Nothing an agent needs to call it safely is missing.

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 coverage is 100% and the schema already explains both parameters, so the baseline is 3. The description adds meaning beyond the schema by tying approveBroadcast to the FOUR02_COMMERCE_PAYER_KEY prerequisite and reiterating the human-approval gate in context.

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?

States a specific verb and resource ('verify a signed 402 invoice and build the exact USDC payment plan'), which is clearly distinct from siblings like four02_invoice_create and four02_invoice_status. An agent can tell what this tool does without opening the schema.

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?

Explicitly states the default behavior (dry run, broadcasts nothing) and the precise conditions for the alternative (approveBroadcast:true only after explicit human approval of that exact payment, and only when FOUR02_COMMERCE_PAYER_KEY is configured). Both when-to-use and when-not-to-use are covered.

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