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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real behavioral detail beyond them: results are ordered most-recent-first and returned grouped as one line per conversation, which tells the agent what the payload looks like. Pagination behavior is left to the schema's pg/qtd parameters.

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 compact sentences with zero filler. The core listing behavior and its output shape are front-loaded, and the usage hints follow as a secondary sentence.

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 read-only, six-parameter listing tool with no output schema, the description covers what it returns and how results are ordered and grouped. Combined with full schema coverage and the annotations, an agent has what it needs to invoke it correctly, though a note on result-limit/truncation behavior would seal it.

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 every parameter is already documented in the schema; baseline 3 applies. The description hints at filtro ('não lidos') and periodo ('hoje') and at the conversa grouping, but adds no syntax or semantics beyond what the schema enums already state.

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 ('Lista') and resource ('emails de uma pasta') plus ordering ('mais recentes primeiro') and output shape ('uma linha por conversa'). It implicitly contrasts with the search sibling 'find', though it never names it, so sibling differentiation is only partial.

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?

Gives concrete usage contexts ('ver a caixa, não lidos, emails de hoje etc.') that map directly onto the filtro and periodo parameters. It stops short of stating when to prefer a sibling such as find over this listing tool, so no explicit alternatives are offered.

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