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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely new behavioral context: a 60-minute cache and the size of the returned description field (~1,500 vs 6,000 characters with detail 'full'). It doesn't cover not-found/error behavior.

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?

Purpose and lookup keys are front-loaded in the first clause, with the return-field inventory after and the cache note last. The single sentence inventories many fields but each item is concrete and non-redundant, so it stays informative rather than 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 no output schema, the description carries the return-value burden and does so exhaustively (status, dates, funding, eligibility, contacts, documents, official URL), plus caching. It omits what happens when neither identifier is supplied or when the id doesn't exist, which matters given zero required parameters.

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 67%, and the description compensates for the gaps: it decodes opportunity_id ('digits at the end of a listing URL') and explains the practical effect of the detail enum (description length). opportunity_number's semantics are still left largely to the schema's example.

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 ('Get one Grants.gov listing in full') and pins down the lookup key (opportunity id or opportunity number). The singular 'one ... listing' cleanly distinguishes it from the sibling search_grants, which lists many.

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?

Explains where the identifier comes from ('the digits at the end of a listing URL') and gives a format example for the number, so an agent can tell which input it must already have. It does not explicitly state when to prefer this over search_grants or eligibility_explainer, so it stops short of full routing guidance.

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