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

Annotations already declare readOnlyHint/idempotentHint and destructiveHint=false, so the safety profile is covered; the description adds real context beyond that — 'Grátis' (no cost), how null field values should be interpreted, and the downstream consequence that an alert per CNPJ won't use such a CNAE.

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?

Four dense sentences with the core purpose front-loaded and no filler; each sentence adds a distinct behavioral fact. It is appropriately sized for a two-parameter tool, though it slightly blurs description vs schema content.

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 name the returned fields (description, family, coverage indicators). For a simple read-only, free suggestion endpoint the description covers modes, defaults, and edge cases, leaving only minor gaps like pagination/limits.

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 both parameters are already documented and the baseline is 3. The description adds value above that by giving concrete `q` examples (`1412`, `1412-6/01`), clarifying prefix-vs-word matching, and describing the default listing behavior when `q` is absent; `limite` itself is left to 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+resource: search-term suggestions for economic activity (CNAE), explicitly listing what comes back (description, family, coverage indicators). It does not contrast itself with any sibling, but the CNAE domain is distinctive enough that an agent can identify it without opening the 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?

It spells out the two operating modes conditionally — without `q` it lists activities with the most registered suppliers, with `q` it searches by code prefix or description word — and gives the edge-case semantics (null `familia`/`termos` means the CNAE is not in the dictionary and a per-CNPJ alert skips it). Clear context, but no explicit when-not or alternative-tool routing.

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