CPFHub.io

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

With no annotations, the description carries the full burden. It discloses the key behavioral fact that authentication via API key is required and characterizes the data as a public read set, but says nothing about rate limits, error behavior, or whether the call has side effects. Adequate but incomplete for a tool with zero annotation coverage.

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 with zero filler. The data-scope statement is front-loaded and the auth requirement follows immediately; nothing could be trimmed without losing information.

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?

There is no output schema, so the description must summarize returns, which it does by naming the data set (credit balance and plan). For a one-parameter, read-only quota tool this is nearly complete, with only return-format or pagination detail missing.

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% and the single api_key parameter is fully documented in the schema, including that it is optional if already supplied via the x-api-key header. The description only restates the auth requirement, adding no syntax or format detail beyond 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?

States a specific verb and resource: returns credit balance and plan data. It is clearly distinct from the sibling CPF lookup tools, though it does not explicitly name them to reinforce the distinction. A precise endpoint equivalence (GET /quota) anchors the purpose.

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 the use case (checking balance/plan) but never states when to call it versus the lookup_cpf siblings, nor any preconditions beyond auth. The endpoint equivalence gives indirect context but no explicit when/when-not guidance.

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

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

No annotations are provided, so the description carries the full burden. It usefully discloses the auth requirement (API key via x-api-key) and the shape of the return data, which is valuable given there is no output schema. It says nothing about rate limits, cost, error behavior, or data freshness relative to the realtime sibling.

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?

Three short sentences, front-loaded with the purpose, then the return values, then the auth requirement. No filler and nothing redundant.

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 low-complexity two-parameter tool with no output schema, the description covers purpose, return fields, and auth. The one material gap is the failure to differentiate from lookup_cpf_realtime, which an agent would need in order to choose correctly.

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 fully documented in the schema, including the accepted CPF formats and the optional-header fallback for api_key. The description adds no syntax or format detail beyond the schema, so the baseline 3 applies.

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?

States a specific verb and resource ('Consulta informações de um CPF brasileiro na CPFHub.io') and enumerates the returned fields (nome, data de nascimento, gênero). However, it does nothing to distinguish itself from the sibling 'lookup_cpf_realtime', which strongly implies a cached/database vs. real-time distinction that the description never addresses.

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 when-to-use guidance is given. The presence of 'lookup_cpf_realtime' as a sibling makes the missing selection criteria a real problem — an agent cannot tell which CPF lookup to pick. The description only notes that an API key is required, which is a prerequisite, not usage guidance.

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

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

With no annotations, the description carries the full burden and does well: it discloses that mismatch/nonexistent CPFs return errors (birth_date_mismatch, cpf_not_found) without charging credits, that deathYear is always present, and that API key auth is required. It does not disclose rate limits, credit cost on success, or return format, but this is solid behavioral context.

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 sentences, each earning its place: source, return, error behavior, requirements. Slightly dense but front-loaded with the core purpose and no filler.

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?

No output schema, but the description summarizes return fields (dados cadastrais, situação, deathYear) and error codes, and covers auth. It is complete enough to invoke correctly, though a bit more on credit cost on success or return shape would fully close the gap.

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 coverage is 100% and all three parameters are described in the schema, including api_key's optionality and the two date formats. The description adds auth requirement context but no parameter syntax beyond what the schema provides – baseline 3 is appropriate.

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?

States a specific verb+resource ('Consulta um CPF brasileiro em tempo real na Receita Federal pela CPFHub.io') and names the data source. Distinguishes from sibling 'lookup_cpf' via 'em tempo real' (real-time vs presumably cached/batch) and 'Receita Federal', though it doesn't explicitly contrast with the sibling.

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?

Implies usage via the real-time Receita Federal source and the required birth_date, but does not state when to prefer this over 'lookup_cpf' or 'get_quota_info'. The error conditions hint at constraints but usage context is left to inference.

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