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

Annotations already indicate readOnly, idempotent, and non-destructive behavior. Beyond that, the description adds important behavioral context: it validates only check digits, does not reveal the holder's identity, and also reports identity broker availability. This is useful context beyond the annotations, though it does not detail output format or edge-case behavior.

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 exactly two sentences, front-loads the main purpose, and includes only relevant information. Every part is meaningful: what is validated, how, the availability check, and the privacy guarantee. No wasted words.

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?

For a single-parameter read-only validation tool with strong annotations, the description provides enough context to select and invoke the tool. It explains the core function, the privacy constraint, and the added availability check. It could briefly mention the return value, but the simplicity of the tool reduces the need for more detail.

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 schema provides only the parameter name 'cpf' and type 'string', with no description. The tool description adds the meaning that this CPF string is used for validating check digits via mod 11, but it does not specify accepted formats (e.g., with/without punctuation, length) or what happens with invalid input. This is a moderate improvement over the bare 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 uses a specific verb ('Valida') and names the exact resource (CPF), plus the method (dígitos verificadores mod 11). It also states the secondary purpose (identity broker availability), which clearly distinguishes the tool from siblings like authenticate and cpf_processos.

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 implies this tool should be used when someone needs to validate CPF check digits, but it does not explicitly state when to prefer it over sibling tools or when not to use it. There is no mention of alternatives or exclusions, so usage guidance remains only implicit.

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