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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false. The description adds meaningful behavior beyond those: it performs a live GET against the public IBGE Localidades API, returns a Markdown list, uses mesoregion as a geographical proxy, and can optionally include population data. It stops short of a 5 because the raio parameter creates some ambiguity about whether the mesoregion approximation is always used.

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 well structured with features, examples, and a behavior note, and it front-loads the core purpose. However, the limitation about mesoregion being an approximation is stated twice ('Uses mesoregion as geographic proximity proxy' and later 'proximity is approximated by shared mesoregion'), which is redundant and costs it a higher score.

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 4-parameter tool with strong annotations and a 100% schema coverage, the description is largely complete: it covers input modes, output format, read-only behavior, limitations, and an alternative tool. The main gap is that the raio parameter is absent from the narrative description, leaving its relationship to the mesoregion-based behavior unexplained.

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 input schema already explains each parameter, including the 7-digit code and the requirement for uf when using a municipality name. The description adds useful examples but no deeper semantic detail beyond the schema, and it never mentions the raio parameter even though it is part of 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?

The description opens with a clear verb and resource: 'Finds nearby/neighboring municipalities.' It further clarifies the exact mechanism (same mesoregion as a proximity proxy) and differentiates itself from ibge_municipios by stating that listing/searching municipalities should use that sibling tool.

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 explicit routing guidance: 'For listing/searching municipalities, use ibge_municipios' and notes that exact spatial neighborhood would require mesh processing. It also gives concrete examples for code-based, name-based, and population-included calls. It does not explicitly enumerate all alternative tools, but the guidance is clear and actionable.

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