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

With readOnlyHint=true already covering the safety profile, the description adds genuinely useful context: pagination size (100 per page) and the vendor quota (60/min, 1000/24h) plus the note that each call consumes one request. That quota framing is exactly the sort of operational detail annotations do not provide; it stops short of describing the response envelope, but the field list partially covers that.

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?

Four compact sentences, front-loaded with purpose and resource identifier before the filtering and rate-limit details. Dense but every clause carries information; only the field enumeration slightly overlaps with the schema.

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 10-parameter paginated read with no output schema, the description compensates by listing returned fields and explaining pagination and quota limits. Annotations cover safety. It is close to complete; a note on how the response exposes the next page number would close the last 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?

Schema description coverage is 100%, so all 10 parameters are already documented in the schema, including enum values and date formats. The description merely restates the filterable dimensions and does not add syntax, defaults, or interactions beyond what the schema provides, 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 (list) and a precisely scoped resource (purchase/vendor invoices), explicitly contrasted with the sibling sales-invoice tool via the '(vendor)' qualifier. It also enumerates the returned fields (number, vendor, dates, amounts, VAT, outstanding amount, optional rows), so an agent knows both what it fetches and roughly what comes back.

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 usable filter dimensions (date, vendor, number, payment status with unpaid/overdue) but gives no explicit when-to-use guidance or routing against alternatives like list_sales_invoices. Usage is implied by the resource name rather than stated, leaving the agent to infer selection.

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