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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds the mode-switch behavior (single read by id returning line items), but says nothing about pagination limits beyond 50, ordering for the id path, or the shape of the response — little beyond what the annotation and schema pair already conveys.

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?

The purpose and dual mode are front-loaded in the first sentence, with the illustrative questions trailing as supporting context. It is one tight pair of sentences with no filler, though the example-question sentence is somewhat redundant with the already-explicit scope statement.

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 an output schema present (return fields need not be explained) and annotations covering the read-only safety profile, the description supplies everything else an agent needs: scope, the id-based single-read mode, supported filters, and representative question phrasings for selection.

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 id, limit, status and clientId parameters each carry their own semantics in the schema, including the enum meanings and the id override rule. The description contributes no additional parameter detail such as id formats or clientId sources, 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 and resource ('Lists company invoices'), and additionally spells out the dual behavior: a filtered list with status/amount/due-date fields, or a single invoice with line items by id. This clearly separates it from siblings like list_deals, list_projects, or forecast_cash_flow without needing the schema.

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 four example questions ('what invoices are outstanding?', 'what is overdue?', 'what does this client owe us?', 'which invoice has been unpaid longest?') give concrete selection context for the agent. It stops short of naming an alternative tool or stating when not to use it (e.g. versus get_project_profitability or forecast_cash_flow), so it is clear context without exclusions.

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