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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), yet the description adds real operational context: filtering by data de publicação, mandatory modalidade at PNCP, and the crucial caveat that an empty list only means 'nada publicado' when fontes[0].status is ok. It does not describe pagination behavior beyond what the schema already documents.

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 what the tool returns, then caveats and exclusions; every clause carries information. It is dense and slightly run-on, but there is no filler or restated boilerplate.

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 an output schema exists (return values need not be explained) and annotations cover safety, what remains for the description is source, filter semantics, mandatory params, non-coverage and empty-result interpretation — all present. An agent has everything needed to call this correctly or pick the sibling instead.

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 explains pagina, cnpj_orgao, date window/366-day limit and the full modalidade code table. The description reinforces that modalidade is obligatory but adds no syntax or format detail beyond the schema, which is exactly the baseline-3 case.

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 resource and scope: licitações e compras diretas publicadas por um órgão, com os campos retornados (objeto, valor estimado/homologado, situação, link). It also names the sibling it is not (contratos_do_orgao) and the source of truth (PNCP), so an agent can distinguish it from contratacoes_abertas and contratos_do_orgao 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 when to use ('Use para conhecer o histórico de compras de um órgão') plus explicit exclusions ('NÃO cobre: compras fora do PNCP, fornecedores vencedores (veja `contratos_do_orgao`), nem busca por texto'). It even routes to the correct sibling by name, which is the strongest form of alternative guidance.

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