Read a message

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

Despite strong annotations (readOnlyHint, idempotentHint), the description adds important behavioral context: body truncation at max_chars, the body_truncated flag, and a security warning that message bodies are untrusted. This goes well beyond what annotations convey.

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 efficiently structured: a one-line purpose, a short truncation note, a security warning, and a concise return-field list. Every sentence contributes meaning without unnecessary fluff.

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 fetch tool with no output schema, the description fully documents return fields, truncation behavior, and security considerations. Together with the annotations and schema, it gives an agent everything needed to invoke and interpret the tool correctly.

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%, so both parameters are already well-documented. The description reinforces the handle source and max_chars default/truncation behavior, but does not add major new meaning beyond the schema. This is a solid baseline score.

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 opens with a specific action ('Fetch one message in full') and names the exact resource (a message identified by a handle from apple_mail_search_messages). It clearly distinguishes this read tool from sibling tools like search, list, and compose.

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 clearly indicates the tool is used after apple_mail_search_messages, providing a concrete workflow. It does not explicitly state when not to use it or mention alternatives like apple_mail_unread_summary, but the context is sufficiently clear for an agent to select it appropriately.

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