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

Beyond the annotations (readOnly, idempotent, non-destructive), the description discloses important behavioral traits: no credentials, pay-per-use with prepaid credit, and that the data is public non-confidential information with LGPD compliance. This adds substantial context about access, cost, and legal use, exceeding what annotations provide.

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 three sentences: the first states the core purpose, the second explains access/payment, and the third covers legal/LGPD. While concise, the third sentence could be seen as secondary but still relevant. Overall it is well-structured and front-loaded.

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 simple tool with two parameters and no output schema, the description covers purpose, access model, payment, and legal compliance, but omits the meaning of the 'completo' parameter and does not describe the return format. The gaps are notable but not fatal given the tool's simplicity.

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 has two parameters (Cnpj, completo) with no descriptions, and the description only references 'CNPJ' without explaining the 'completo' boolean. Schema coverage is 0%, so the description fails to clarify the optional parameter's meaning, leaving a critical gap.

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 clearly states the tool's function: 'Emite o Certificado de Regularidade do FGTS (CRF) de um empregador a partir do CNPJ.' This is a specific verb, resource, and input. It distinguishes itself from unrelated siblings (authenticate, connect, marketplace, etc.) by being the only tool for FGTS certificate issuance.

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 provides clear operational context: hosted by the platform, no credentials required, prepaid credit per query, and it accesses public information. It does not explicitly mention alternatives or exclusions, but the context is sufficient for an agent to decide when to use this tool.

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