rd

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 genuinely useful behavior beyond that: the returned body is post-processed (citations, signature and legal notice stripped) and thread mode expands to the full conversation, so the agent knows the output is not the raw message. Missing: behavior for invalid/already-deleted targets and whether the read marks the message as read (the 'atual' pointer implies state changes on read).

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 clauses, front-loaded with the main action, with zero filler. It is terse to the point of omitting useful routing information, but nothing present is wasted.

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 2-parameter read tool with full schema coverage and read-only annotations, the description covers what is returned (cleaned body) and the thread variant. It lacks only edge-case behavior (unknown id, side effects on the read/unread state), which is minor given the structured fields already supplied.

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%, with both parameters documented, including the three enum values of modo. The description only echoes the thread mode, adding no syntax or format detail beyond the schema, so 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 ('Lê um email') and adds a distinguishing detail: the body returned is cleaned of quotes, signature and legal disclaimer. This is enough for an agent to tell it apart from listing/searching siblings like ls and find, though no sibling is named explicitly.

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?

Usage is implied by the resource (read one email by short id or the 'atual'/'ultimo' pointers), and the description notes thread mode shows the whole conversation. It never states when to prefer this over att (attachments) or rp, nor any exclusions or error conditions.

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