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

Goes well beyond the annotations (readOnlyHint=false, idempotentHint=true) by disclosing the 30-minute link expiry, that the reservation is released if unpaid, that the tool does not itself take payment, and the Canada CAD fixed-rate behavior returned as charged_amount_cents. These are exactly the operational facts an agent cannot get from the structured fields.

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?

Five tight sentences, front-loaded with the core action and outcome, followed by expiry, payment boundary, currency note and idempotency. No sentence is filler; each carries a distinct operational constraint.

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 mutation tool with no output schema, it covers the important behavior (expiry, reservation, payment boundary, idempotency) and even names one return field (charged_amount_cents). It stops short of describing error/failure responses or the full returned link structure, leaving a small gap.

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 75%, covering agent, ship_to and client_request_id, and the description reinforces client_request_id's retry semantics and explains that ship_to drives the Canada CAD conversion. It adds real meaning (currency/charging consequence of ship_to) beyond the schema, though it does not spell out the per-item quantity caps or items array shape.

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 precise verb and resource ('Reserve stock ... and return a Stripe Checkout link') along with the concrete two-step outcome. The sibling tools are all read/retrieval operations, and this is unambiguously the write/payment-initiation path, so it is easy to separate from them.

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?

Gives clear context for when to call it and an explicit exclusion ('Shipping address, name and phone are entered on the Stripe page — do not collect them yourself'), plus idempotency guidance for retries. It does not name a comparative alternative, but none exists among the read-only siblings, so the guidance is effectively complete.

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