Get Message

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds only that the result may be a 'summary or detail', without explaining what determines which, or mentioning the conditional-request/304 behavior that the schema documents. With annotations carrying most of the load, this is adequate but thin.

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 with zero filler; the primary action comes first and the fallback routing follows immediately. Every clause earns its place.

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?

With a rich annotation set and an output schema, the description does not need to explain return values, and it correctly flags the body-content alternative. The only real gap is the unexplained 'summary or detail' distinction, which leaves the agent unsure what it will receive from a given call.

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%, so mailbox_id, message_id and If-None-Match are already documented, including the multi-mailbox targeting rule and the ETag semantics. The description adds no parameter-level meaning beyond restating message_id, so the 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: fetch one message by message_id, and clarifies the scope is a single message. It distinguishes itself from the body-reading siblings (mailbox_list_body, mailbox_list_content) but does not differentiate from other near-neighbors such as mailbox_batch_get_messages or mailbox_get_thread, which an agent must still infer.

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 routes the agent away from this tool when full body content is required, naming the two alternatives to use instead. It gives no guidance for the multi-message case (batch_get_messages) or thread retrieval, so the routing is clear but not exhaustive.

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