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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds the specific input format (44-digit key), but does not describe return format, error handling, or any additional behavioral aspects like rate limits or authentication requirements. With annotations providing safety guarantees, a score of 3 is appropriate as it adds some but not rich 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?

The description is a single, concise sentence in Portuguese that directly conveys the tool's purpose and key parameter. It is front-loaded with the action and resource, and no unnecessary information is included. Perfectly efficient for its task.

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?

Given the tool's simplicity (one parameter, no output schema, annotations covering safety), the description is adequate but leaves gaps: no mention of what is returned on success/failure, any validation requirements for the key, or whether there are restrictions on usage. For a simple lookup tool, this is acceptable but could be more complete.

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 0%, so the description must compensate. It does: it specifies that the parameter is a chave de acesso with 44 digits, which adds meaning beyond the raw schema ('nfe': string). However, it does not specify whether the parameter is the full key or part, or how the key should be formatted. Since there is only one parameter and the description explains its semantics, a baseline of 3 is fair.

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 purpose: 'Consulta uma Nota Fiscal Eletrônica (NF-e) pela chave de acesso (44 dígitos).' It names the specific resource (NF-e), the action (consulta), and the key parameter (chave de acesso de 44 dígitos). This distinguishes it from sibling tools that query other types of data (e.g., consultas_cpf, consultas_fgts).

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 implicitly indicates that the tool is used when needing to query an NF-e, but it does not explicitly state when to prefer this tool over alternatives or any prerequisites (e.g., authorization, format validation). The sibling list shows many similar consultas_* tools, but the description does not clarify how to choose among them beyond the specific resource type.

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