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

Beyond the readOnly/idempotent annotations, the description discloses the upstream 404 incident, the corrected query signature, the _erro_upstream fallback instead of exceptions, and the 10-minute cache. It also notes useful response fields such as precoUnitario, quantidade, dataCompra, fornecedor, and UASG. This is substantial behavioral context beyond 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 purpose, endpoint, and alternatives before the changelog. The upstream break history is detailed and slightly longer than strictly necessary, but it is relevant to correct invocation and troubleshooting. Overall it is structured and every paragraph serves a purpose.

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?

Given the output schema exists and annotations cover safety, the description is complete for an agent to invoke the tool correctly. It covers the endpoint, required CATMAT code, sibling alternatives, expected response fields, cache behavior, and the known 404 failure mode with its fallback diagnostics.

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 already covers 100% of the parameters with clear descriptions, so the baseline is 3. The description adds route-level context about codigoItemCatalogo and the API's 404 behavior for missing required parameters, but it does not materially enrich the meaning of the individual parameters beyond the schema.

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 description states a specific verb and resource: it searches prices practiced in government material purchases (CATMAT), and explicitly identifies itself as the tool that returns unit prices for materials. It also distinguishes itself from compras_detalhar_preco_material, which it says does not return prices.

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 gives explicit routing guidance: use compras_pesquisar_precos_para_etp for consolidated statistical views (IN 65/2021 averages/medians), and warns that compras_detalhar_preco_material does not return price. This clearly tells an agent when this tool should and should not be chosen.

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