Read Message Content

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

Annotations already declare readOnly, idempotent, non-destructive, openWorld, so safety is covered. Beyond that the description adds essentially nothing: it does not mention truncation via max_body_chars, the 304 conditional-response behavior, or that attachment contents are never returned — all behaviors an agent would want highlighted.

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 sentences, front-loaded with the primary use case and followed by a preference condition. Nothing is redundant, though the second sentence is vague enough that it earns only partial credit.

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?

An output schema and full parameter documentation exist, so much of the burden is off the description. Still, for an 11-parameter read tool the description never characterizes what 'structured content' contains or how truncation/conditional requests behave, leaving the definition minimally adequate.

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 description coverage is 100% with 11 well-described parameters including enums for part, include_headers, and include_attachments. The description adds no parameter meaning at all, so the schema baseline of 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 ('read structured content for a known message_id'), which distinguishes it from search/discovery tools that take query terms rather than an ID. It does not, however, separate it from nearby siblings such as mailbox_get_message or mailbox_list_body, which likely also return message content.

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?

'Prefer it when headers, participants, or body parts affect the answer' gives a positive selection condition, but no alternative is named and no exclusion is stated. An agent must still infer whether to call this or get_message/list_body.

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