download_attachment

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

Goes well beyond annotations: explains it returns paths and SHA-256 rather than bytes, discloses no overwrite, no read-marking, a 40 MiB parsing ceiling with no separate file cap, and a security warning about untrusted downloads. These are exactly the non-obvious traits the structured fields cannot express.

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?

Five tight sentences, front-loaded with the action and source, then return shape, then behavioral and safety notes. Every sentence earns its place with no repetition of schema or annotation content.

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 5-param download tool with no output schema and readOnlyHint=false, the description covers return format, overwrite policy, size limits, and the security posture. Nothing an agent needs to call it safely and correctly is missing.

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 60%; the description clarifies that the index is zero-based and originates from list_attachments/get_email, and that save_as never overwrites. It does not describe uid, uid_validity, or mailbox semantics beyond the schema, so it modestly exceeds schema-level info without fully covering all 5 params.

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+resource ('Save one attachment') and ties it to the sibling tools that produce its input ('from list_attachments or get_email'). This distinction lets an agent route the attachment_index value correctly without opening either schema.

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?

Names the two upstream tools (list_attachments, get_email) and the index they supply, making the workflow sequence clear. It lacks an explicit exclusion, e.g. when to prefer list_attachments metadata over a download, but the context is specific enough for correct invocation.

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