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

The readOnlyHint annotation already establishes this is a safe, non-mutating read, so the description's burden is reduced. It adds the useful detail that this maps to GET /api/v1/expenses, but says nothing about pagination behavior, result ordering, or the response shape.

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 short sentences with the capability statement front-loaded and the API endpoint trailing — no filler or repetition. It is efficient, though the extreme brevity leaves the definition doing little work beyond the structured fields.

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 an 8-parameter list tool with no output schema, the agent still lacks any description of what an expense record contains or how results are paginated/ordered, which the description does not address. The fully documented schema and the readOnlyHint annotation compensate for most of the gap, keeping this at a minimum-viable level.

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 8 parameters are already documented in the schema with formats, ranges, and examples (e.g., sort syntax, status values). The description's note about client and invoicing/payment-state filters loosely maps to client_id and client_status but adds no syntax or semantics beyond the schema, so 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 ("List expenses") and names the filter dimensions (client, invoicing/payment state). It does not distinguish itself from sibling list tools such as invoiceninja_list_invoices or invoiceninja_list_payments, but the noun 'expenses' makes the target unambiguous.

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 mention of client and invoicing/payment-state filtering implies when the tool is useful, but there is no explicit when-to-use or when-not-to-use guidance and no pointer to alternatives. Adequate but with a clear gap for an agent choosing among ~10 list_* siblings.

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