Fetch a Brazilian establishment's official data from the CNPJ registry using its 14-digit CNPJ, covering status, activity, municipality, size, and capital.
Um estabelecimento do recorte pelo CNPJ de 14 dígitos: situação, atividade, município IBGE, porte, capital.
| Name | Required | Description | Default |
|---|---|---|---|
| cnpj | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description must disclose behavior, but it only describes the resource. It does not state that this is a read-only lookup, what occurs if the CNPJ is not found, whether multiple records could be returned, or any access constraints. The singular 'Um estabelecimento' implies one record, but this is implicit.
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 a single sentence with no filler. The scoping by CNPJ is front-loaded, and the field enumeration is succinct. Every word contributes to conveying the tool's core subject.
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 and no annotations, the description must explain the operation and expectations. It lists some output fields but does not explicitly say this is a lookup operation, does not cover error behavior, and does not situate the tool relative to its siblings. An agent would remain uncertain about the return envelope and failure modes.
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 input schema only defines 'cnpj' as a string with no description. The description adds crucial semantics by specifying the CNPJ must be 14 digits and that it is the selection key for the establishment. This helps the agent construct a valid request, though it does not detail validation rules.
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 identifies the tool as providing an establishment for a given 14-digit CNPJ and lists the included fields (situação, atividade, município IBGE, porte, capital). This distinguishes it from the sibling tools, which handle counting, listing, and data caveats. The lack of an explicit verb like 'retrieve' or 'get' prevents a perfect score.
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?
No guidance is given about when to use this tool versus the siblings. There is no mention of selecting this tool when you have a specific CNPJ and need establishment details, nor any exclusion of alternatives. The agent must infer the usage context from the resource-focused description.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.