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

readOnlyHint=true already declares the safety profile, so the description only needs to add context. It adds the per-invoice scoping and the underlying endpoint, but says nothing about pagination, ordering, or what an empty result means for an invoice with no payments.

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 with the purpose front-loaded and no filler. The trailing API route line is mildly developer-oriented and adds little for an agent deciding whether to call the tool.

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 tool with annotations and no output schema, the definition covers what is needed to invoke it correctly. A brief note on the returned payment fields or result ordering would close the remaining 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?

With one parameter at 100% schema coverage, the schema already documents invoice_number. The phrase 'one vendor invoice' usefully reinforces that this is a vendor (not customer) invoice number, but no format, example, or lookup hint is added.

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 (list) and a precisely scoped resource (payments booked against one vendor invoice), which implicitly separates it from runmyaccounts_list_invoice_payments and runmyaccounts_list_payments_since. No sibling is named explicitly, so differentiation is inferred from the 'vendor invoice' qualifier rather than stated.

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 never says when to use this versus runmyaccounts_list_payments_since (date-based) or the customer-invoice counterpart, nor does it state prerequisites such as needing a valid invoice number first. Usage is only inferable from the tool's purpose.

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