read_message

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

Discloses read-only nature, security warning about body content, and max_chars behavior including truncation indicator and re-reading advice. This compensates for lack of 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?

Well-structured with clear sections but slightly verbose. Could be trimmed slightly without losing clarity, but all sentences add value.

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?

Covers usage, parameters, and behavioral aspects well. Lacks explicit return structure but mentions truncation indicators. Good given no 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?

Despite 0% schema coverage, the description thoroughly explains message_id (from search_mail) and max_chars (default, behavior, and practical note about email length). Adds significant meaning beyond 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?

Clearly states the tool reads one message including body, read-only. Distinguishes from sibling tools like search_mail by specifying it is for individual messages already identified by the user.

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?

Explicitly says to call only for user-requested messages, one at a time, never in a loop, and to use search_mail first for candidates. Also provides security guidance on treating body as data.

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