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

readOnlyHint=true already declares this as a safe read, so the description's burden is light. It usefully clarifies that both 'pay_' and 'sid_' identifiers are acceptable and maps to the concrete REST endpoint, but says nothing about error behavior (e.g. not-found handling) or what the 'full details' payload contains.

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 tight sentences, front-loaded with the core action and followed by the identifier format and endpoint mapping. Nothing is padded and no sentence is redundant.

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 one-parameter read tool with a readOnlyHint, the essential facts (what it fetches, by what id, against which endpoint) are present. The absence of an output schema means the shape of the returned payment details is unspecified, a minor gap the description does not attempt to close.

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% with a single well-documented id parameter, so the schema already carries the semantics. The description's example prefix ('pay_...') and session-id note largely restate the schema, meeting the baseline of 3 without adding new syntax or format rules.

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+resource (get the full details of a payment) and clarifies it also accepts a payment session id, with the underlying endpoint GET /payments/{id}. It distinguishes itself implicitly from list/search siblings by being an id-based single-record fetch, though it never names those alternatives.

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?

Usage is implied: you call this when you already have a payment id. There is no explicit guidance on when to prefer this over checkout_search_payments, checkout_get_payment_actions, or checkout_list_payments, and no stated preconditions or exclusions.

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