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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description usefully adds that the applied_to relationship data is included via the include parameter, but says nothing about not-found behavior or response shape beyond that field.

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 tight sentence plus the raw endpoint template, front-loaded with the resource and scope. No filler, nothing 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?

With no output schema, the description carries the return-value burden and partially does so by naming the applied_to expansion. For a simple single-entity GET with covered annotations and a fully documented param, this is nearly complete, though it omits error/empty cases.

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 the single payment_id param is already documented in the schema, so the baseline is 3. The description adds only that the fetch expands applied_to, which is more a return-value note than a parameter semantic.

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 one payment by id) and adds scope by naming the applied_to expansion, which surfaces which invoices/credit notes the payment settled. It does not explicitly distinguish itself from invoiced_list_payments, but the singular framing makes the difference inferable.

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 by the singular 'One payment by id' framing versus the list sibling, but there is no explicit when-to-use, when-not-to-use, or prerequisite statement (e.g., payment must exist, use list_payments to discover ids).

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