gmail_export_message

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

Annotations already declare readOnly, idempotent, and non-destructive, and the description reinforces that with "Read-only." It adds genuinely new behavior not in the annotations: a size guard ("Refuses payloads over MAX_ATTACHMENT_BYTES × 25") and the base64url encoding the caller must decode. It stops short of saying what happens on refusal (error shape) or whether attachments are inlined.

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?

Four short clauses, zero filler. Output format, downstream use, size limit, and safety profile are all front-loaded, with nothing repeated from the schema.

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 single-parameter read tool with no output schema, it covers the essentials: return encoding, how to interpret the bytes, a hard size ceiling, and confirmation of read-only behavior. A note on the refusal error or attachment inclusion would close the remaining gap.

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% for the single message_id parameter, so the schema already carries the meaning and the baseline applies. The description adds no syntax hints for message_id (e.g., hex ID format) beyond what the schema states.

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 ("Exports a Gmail message") plus the exact output format (raw RFC822, base64url), which implicitly distinguishes it from gmail_get_message_details and gmail_preview_message. It never names those siblings explicitly, so differentiation is inferential rather than stated.

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?

"Decode to .eml for backup/forensics" implies when the raw form is the right choice, but the description never states when NOT to use it or points to the sibling that returns parsed message content. Usage is suggested, not routed.

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