request_payment_token

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

With no annotations provided, the description carries the full transparency burden. It discloses that the card is single-use, JIT, locked to one amount and merchant, that passing `cart` creates a signed intent with cryptographic proof, and that a mismatch caught after this point 'costs a card.' It also mentions the prerequisite of reading the SOP, providing rich behavioral context beyond a simple 'request' 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 longer than the calibration examples, but every sentence earns its place: it front-loads the core purpose, then presents critical warnings, timing rules, an alternative, and a safety checklist. The structure is logical and scannable with a clear warning symbol. Slightly verbose but appropriately sized for the tool's high-stakes nature.

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 tool's complexity and the absence of an output schema, the description is nearly complete. It covers prerequisites (SOP), timing, alternatives, safety checks, and the binding behavior. The only gap is that it does not describe the return value (e.g., the shape of the token response), which would be useful since no output schema is present.

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%, so the baseline is 3. The description adds meaningful semantics to the `cart` parameter, explaining it is 'RECOMMENDED' and that it becomes a signed intent bound to the card, which is more than the schema's dry description. However, other parameters like card_alias and merchant receive no extra semantic enrichment beyond the schema.

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 opens with a specific, unambiguous verb+resource statement: 'Request a single-use JIT virtual card ($1–$100) locked to one amount + merchant.' This precisely defines the tool's function and explicitly distinguishes it from the sibling tool auto_pay_checkout by stating when to prefer that alternative.

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 provides explicit when-to-use guidance: 'Only call once the FINAL total is visible' with distinct rules for physical vs. digital goods, and names auto_pay_checkout as the alternative for digital goods. It also mandates reading a SOP resource and includes a pre-request verification checklist, offering clear context and exclusions.

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