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

readOnlyHint=true already covers the safety profile, and the description reinforces it ('this server never records or refunds payments') while adding useful shape information about what is returned, including applied-invoice relationships. It does not mention pagination limits or ordering behavior, keeping it short of a 5.

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 sentences plus an endpoint reference; the return content is front-loaded, the read-only constraint follows immediately, and nothing is redundant or padded.

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 usefully summarizes the return payload and its relationships, and the schema covers all inputs. Minor gap: no mention of pagination/default page size behavior, which matters for a 7-parameter list tool.

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%, so page, sort, filter, number, status, per_page and client_id are already fully documented. The description adds no filtering or pagination semantics beyond the schema, 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?

Specific verb (list) plus resource (payments received) and an enumeration of the returned fields (amount, date, refunded/applied totals, paymentables). This clearly distinguishes it from the many sibling list_* tools and from get_invoice.

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 conveys that this is a read path and notes that the server never records or refunds payments, which implicitly frames usage. However, it names no alternative tool or condition (e.g., when to prefer get_invoice for one payment, or list_invoices for invoice-level views), so routing guidance is left to inference.

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