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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered structurally. The description adds real behavioral context beyond that: a fixed 12-month lookback window, the fact that a paid 24h token is required, and the shape of the payload (supplier CNPJs plus recent contracts). It does not mention rate limits, pagination, or what happens with an expired token, which keeps it below 5.

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?

Two sentences, no filler: the data scope and payload come first, the paid-token prerequisite second. Every clause contributes information an agent needs before calling.

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?

With no output schema, the description carries the return-value burden and does so at a summary level (top suppliers and recent contracts). Combined with fully documented parameters and read-only annotations, an agent has enough to call it correctly; only finer detail like payload structure or pagination is absent.

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%, with both parameters documented in the schema itself, including the 7-digit IBGE code and the token's provenance. The description only reinforces that the tool is scoped to a single municipality; the baseline of 3 applies when the schema carries the parameter burden.

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 names a specific resource (contracts published in the PNCP by a municipality's city hall) with a concrete scope (last 12 months) and content (top suppliers with CNPJ plus recent contracts). It is distinguishable from ranking_municipios and resumo_municipio, but it never names those siblings to draw the boundary explicitly.

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?

Usage is only implied: an agent can infer this is the tool for municipal contract data, and the paid-token prerequisite is stated. There is no explicit when-to-use vs when-to-prefer-resumo_municipio or ranking_municipios guidance in the description itself; the routing hints (buscar_municipio, comprar_acesso, ativar_acesso) live in the schema, not the description.

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