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

Annotations already declare readOnlyHint and idempotentHint, and the description aligns with these by using 'Read'. It adds useful behavioral details about bounded body-character pages, attachment names, and pagination, enhancing transparency without contradicting the annotations.

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 concise and well-structured: the main action is stated first, followed by pagination instructions and the optional ID behavior. No unnecessary words or details are included.

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 simple schema and read-only nature, the description is complete enough for an agent to know how to read mail, paginate through long bodies, and handle the optional ID. It does not cover error cases but that is not essential for basic usage.

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?

The input schema covers all three parameters with descriptions, giving a high baseline. The description adds extra meaning for the 'id' parameter (omitting it retains the legacy inbox summary) and reinforces the purpose of 'limit' and 'offset' through pagination context.

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 reads correspondence by ID with pagination, using the verb 'Read' and specifying the resource and scope. It also distinguishes itself by noting that omitting the ID yields the inbox summary, differentiating it from mail_search and mail_inbox.

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 gives practical instructions on pagination ('Follow the returned offset') and the effect of omitting the ID, but it does not explicitly contrast with alternative mail tools like mail_search or mail_inbox. Usage guidance is implied rather than explicitly stated.

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