Calculate invoice deadlines (customer API key)

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

Goes well beyond the annotations: names the exact credential required, states that no request is made without it, enumerates the 401/403/429 failure modes, and discloses the billing side effect ('successful calculations consume one API plan unit'), which is consistent with readOnlyHint=false and destructiveHint=false. Null/empty-value semantics and the 'not legal advice' disclaimer round out the behavioral picture.

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 credential precondition is front-loaded where it matters most, and the long middle sentence is justified by the absence of an output schema. The enumerated return-field list is dense and could have been tightened, but every clause still carries information.

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 and five parameters, the description fully compensates: it documents the return field set, null and empty-list conventions, error classes, billing cost, and legal disclaimer. An agent can call this correctly and interpret the response without further documentation.

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 all five parameters are already documented with formats and examples. The description reinforces that deadlines count from the invoice or delivery date and that project_type/state drive the result, but adds no syntax or validation detail 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: calculates preliminary notice and lien filing deadlines for one construction invoice, with state and date inputs named. It partially distinguishes itself from the supplier siblings only indirectly, via the 'customer key' requirement, and never names calculate_supplier_deadlines or the state-guide tools as alternatives.

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 auth precondition ('requires LIENDEADLINE_API_KEY... without one it returns a configuration error and makes no request') implicitly tells the agent when this tool will work, but there is no explicit when-to-use vs. when-not, and the closely related siblings (calculate_supplier_deadlines, calculate_supplier_deadlines_v3, get_state_lien_guide) are never referenced.

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