mail_read_message

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

Beyond the annotations (readOnlyHint, openWorldHint), the description explicitly states that it does not mark messages as read, does not fetch images, and does not execute content. This provides additional transparency about side effects and safety, which is valuable.

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 extremely concise, using only two sentences to convey the core functionality and exclusions. Every word contributes to the meaning, and there is no redundant or extraneous information.

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, the description provides a reasonable overview of what is returned (bounded content and attachment metadata) and what is not done. However, it does not elaborate on the structure of the response or potential error behavior, leaving some ambiguity for a tool without an output schema.

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 description does not mention any of the three parameters (accountId, messageId, maxBodyChars). Schema coverage is 0%, and the description fails to compensate by explaining the meaning or purpose of these parameters. This is a significant gap.

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 a single message by ID, and specifies that it returns bounded content and attachment metadata. It also explicitly lists what it does not do (mark read, fetch images, execute content), which helps distinguish it from other mail-related tools in the sibling list.

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 some implicit guidance by stating what it does not do, but it does not explicitly mention when to use this tool versus alternatives like mail_read_conversation or mail_search. There is no explicit 'use this when' statement.

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