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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real behavioral context: the exact shape of the returned records and the fact that amounts are unitless with no currency, which no annotation or schema 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?

Three dense sentences, each earning its place: scope, sibling disambiguation, filters/currency caveat. Nothing is repeated from the schema or annotations.

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 no output schema, the description supplies the returned field list and the currency caveat, which is exactly what an agent needs. Sibling disambiguation plus filtering guidance makes it complete for a list tool.

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 the baseline is 3. The description adds a small amount of routing value by naming the filter axes (project, work order, cost category) and by clarifying the semantics of the amount field returned, though it does not go beyond the schema on search/pagination.

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 project-scoped expenses') and pins the exact UI location (Project → Costs → Expenses). It clearly distinguishes itself from the sibling list_asset_costs by naming the differing fields (invoice_number, po_number, category, asset/site links).

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?

Explicitly routes the agent: use this for project-cost-tab expenses, use list_asset_costs for the main AssetLab Expenses page. It also names the filter dimensions and warns to fetch currency_code before stating an amount.

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