check_br_domain

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 clearly describes this as a read-only status check and discloses what it returns (status, suggestions, creation/expiration/last-processed dates for registered domains). This is a non-mutating lookup, and the description effectively communicates the behavioral scope despite lacking explicit safety language.

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 short paragraphs, front-loaded with the core purpose. Concise and to the point. Minor deduction because the second sentence explaining return values could arguably be folded more tightly, but overall it is efficient with no wasted sentences.

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?

Has an output schema and 100% parameter coverage, which reduces the burden on the description. It adequately explains the tool's function and return-value category (status, suggestions, dates). For a one-parameter read-only lookup tool, this is reasonably complete, though it could mention the output schema structure or multilingual/asynchronous behavior if any.

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 parameter 'domain' has a clear example (nubank.com.br). The description reiterates what 'domain' means implicitly. Baseline 3 applies since the schema handles the single parameter well; the description adds no additional formatting rules beyond what the schema example provides.

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?

Clear verb+resource: 'Check the status of a .br domain at Registro.br.' It distinguishes from siblings since it's the only domain-checking tool among lookup/list tools for CNPJ, CEP, DDD, ISBN, etc. The scope (.br, Registro.br) is explicit.

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 usage for checking .br domain availability/status but does not explicitly state when to use it vs alternatives. Given siblings are unrelated lookups (CNPJ, CEP, DDD), differentiation is intuitive, but no explicit when/not-to-use guidance is provided.

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