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

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds substantial context beyond that: it states the tool never returns price, documents the exact 7 upstream DTO fields, confirms via raw call and OpenAPI that the price field never existed, and mentions the 10-minute cache. No contradiction with annotations.

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 description is front-loaded with the most important warning and clearly structured with bold callouts, endpoint, field list, and usage guidance. It is longer than strictly necessary, with some redundant audit detail, but the length is largely justified by the need to correct a misleading tool name and historical docstring.

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?

The description covers purpose, non-goals, the correct sibling alternative, the exact returned fields, the endpoint, cache behavior, and usage boundaries. Combined with a complete input schema and existing output schema, nothing essential is missing for selecting and invoking the tool correctly.

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?

The input schema has 100% description coverage, with all five parameters already documented, including defaults, formats, and an example. The description adds no new parameter-level semantics, so the baseline of 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?

The first sentence states a specific verb and resource: it lists the individual purchases of a CATMAT item. It immediately clarifies the critical scope limitation ('sem valor de preço') and explicitly distinguishes this tool from the price-returning sibling compras_pesquisar_preco_material.

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 description explicitly states when to use this tool ('Use esta tool apenas para: descrição detalhada do item...') and when not to use it, directing price queries to compras_pesquisar_preco_material. This is an ideal when/when-not/alternative structure.

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