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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), so the bar is lower. The description still adds real behavioral value by disclosing the upstream quirk that free text is ignored when a structured filter is present and that the tool resolves query into active_ingredient then brand_name, reporting which in query_resolved_to. Minor gaps remain around pagination/return shape, but the key non-obvious behavior is disclosed.

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 purpose and the scope caveat are front-loaded, and the example questions are compact and useful. The final sentence is somewhat meta ("see the note on query") and mildly redundant with the schema, but the description is otherwise tight for a 12-parameter tool.

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?

No output schema exists, yet the description conveys the domain (Green Book approvals), the disambiguation from sibling lookup tools, the filter set, and the combining edge case. It stops short of describing the return shape or pagination semantics, which an agent would benefit from, but nothing essential for correct invocation 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 100%, so the schema already documents all 12 parameters, and the description's own note on query merely points the reader back to the schema ("see the note on query"). It adds little semantic detail beyond what structured fields provide, so the baseline 3 is appropriate.

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 (search FDA-approved animal drugs in the Green Book) and pins down scope as approval status rather than adverse events or recalls. It also names the siblings it is NOT (vet_adverse_events, vet_product_recalls), so an agent can route without opening any schema.

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?

Explicit exclusions are given with the alternative tool to use instead, representative questions show the intended query shapes, and the description states the query-vs-structured-filter dichotomy and why they do not combine. This is about as clear as when-to-use guidance gets.

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