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

Annotations already declare readOnly/idempotent, and the description adds real behavioral context beyond them: PROJECT-level resolution returning the LATEST fiscal year with metadata.matching_rows, plus error behavior for unmatched ids and the snapshot-cutoff caveat for 'missing' grants. That is exactly the kind of context annotations cannot carry.

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?

Front-loaded with purpose and return shape, then constraints and edge cases in priority order. It is dense but nearly every sentence carries unique information; the final snapshot-cutoff sentence is slightly over-explained.

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?

Even though an output schema exists, the description still previews the response fields and URL purpose, and covers the level-of-aggregation subtlety and failure mode. Nothing an agent needs to call it correctly is missing.

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 0% and the sole parameter is undocumented in the schema, so the description carries the full burden — and does: required, full NIH project number format, regex ^[A-Z0-9-]{1,24}$, a concrete example (1R01CA123456-01A1), and the explicit exclusion of core/partial numbers.

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 ('retrieve the full record for one NIH grant by its id') and discloses the return shape ({id, title, text, url, metadata}). It clearly separates itself from the list/search siblings by being a single-record citation wrapper.

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?

Implies the condition of use (you already hold a full NIH project number) and warns that core project numbers and partial numbers do not match. It does not explicitly name which sibling to use instead when you don't have an id, so it stops short of full when/when-not routing.

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