download_attachment

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

With no annotations, the description carries the full burden. It discloses the return format (base64 content) and a key format constraint for email_id. It does not mention possible errors, authorization needs, or side effects, but the operation appears read-only and the disclosed details add meaningful transparency.

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 a single compact sentence that leads with the action, then gives return format and parameter format. Every part earns its place with no filler or redundancy.

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?

The tool is simple, has an output schema, and the description covers the core invocation details, including the required email_id format. The main gap is the lack of a pointer to get_attachments for obtaining part_id, but this does not block correct invocation when part_id is already known.

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 0%, so the description must compensate. It adds useful meaning for email_id ('folder:uid, e.g., INBOX:1') and identifies part_id as the attachment identifier used for download. It does not explain how part_id is obtained or what its format looks like, leaving part of the burden unmet.

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 clearly states a specific action ('download attachment by part_id') and resource, and adds that it returns base64 content. It does not explicitly differentiate from the get_attachments sibling, but the download-vs-list distinction is reasonably implied by the wording.

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 implies when to use the tool: you need an email_id and part_id, and it provides the email_id format. However, it does not explicitly mention that part_id likely comes from get_attachments, nor does it state when not to use this tool in favor of a sibling.

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