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

The readOnlyHint/destructiveHint annotations already establish that this is a safe read, so the description's added value is the shape of the result: which fields appear per row, the sort order, and that totals accompany the list. It does not disclose a meaningful ambiguity, namely whether the totals cover the full outstanding set or only the returned page (limit defaults to 50, max 100).

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, front-loaded with the returned data and its ordering before the routing hint. No sentence is redundant with another and nothing is 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 only two optional parameters, no output schema, and safety covered by annotations, the description supplies nearly everything needed: scope, per-row contents, ordering, and totals. The only gap is the interaction between limit and the reported totals, which an agent would want to know before summarizing results.

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 coverage is 100%, so both parameters are fully documented structurally, which sets the baseline at 3. The description does add one nuance beyond the schema: 'every unpaid issued invoice' clarifies that the default result includes not-yet-due invoices, which is what makes overdueOnly=true meaningful.

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 precise resource and scope: unpaid issued invoices with remaining balance, days overdue, ordering ('newest due first') and totals. That is far more specific than the name 'fawtar_outstanding' alone, and the phrase 'without composing filters by hand' implicitly contrasts it with the generic fawtar_list, though it never names that sibling.

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 framing 'This is the answer to "who owes me money"' gives a clear triggering question, and 'without composing filters by hand' hints that the alternative is building the same view manually via fawtar_list. No explicit when-not condition or named alternative is given, so it stops short of a 5.

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