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

readOnlyHint=true already establishes this as a safe read, and the description is consistent with that. It adds that payment session ids ('sid_') are also accepted, but says nothing about not-found behavior, error responses, or whether the returned detail set is bounded — minor gaps given the annotation covers the safety profile.

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?

One sentence front-loads the resource and lookup key, followed by a short API mapping. No filler, nothing buried.

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 single-parameter, read-only lookup with a fully documented schema, the description covers what the tool returns at a high level ('full details'). No output schema exists, so a brief return-value characterization is the only remaining nicety, and 'full details of a payment' largely satisfies it.

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 100% and both the format example ('pay_...') and the session-id variant are already documented in the schema. The description's 'pay_...' example is a restatement, so the baseline 3 applies.

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 ('Get'), resource ('payment / payment session'), and lookup key ('by its id'), and even maps to the underlying API (GET /payments/{id}). An agent can distinguish it from checkout_get_payment_actions or checkout_list_payments without opening another 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?

Usage is only implied: you need a payment id, so this is the retrieval path once you have one. It never names alternatives such as checkout_get_payment_actions (for action history) or checkout_search_payments (when you lack the id), so the agent must infer the boundary.

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