save_attachment

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

With annotations only flagging readOnlyHint=false and idempotentHint=true, the description carries the real behavioral load and does so well: mailbox is not modified, an existing target file is silently overwritten (key data-loss risk), tilde is expanded, and missing directories are created. Return contents are also disclosed since no output schema exists.

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?

Purpose leads, behavior follows, then parameters — a sound front-loaded order with essentially no wasted words. The multi-line blank-separated prose layout is slightly heavier than needed for a tool description, but every sentence carries information.

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 no output schema, the description supplies the return values (path, size, MIME type, filename); with annotations covering the safety profile, it adds the overwrite warning and filesystem side effects. Nothing an agent needs to invoke this 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 0%, so the description must carry all five required parameters, and it documents each one: account's source, folder/uid roles, part as a 1-based index from read_email, and save_to's directory-vs-file-path disambiguation with trailing-slash and extension heuristics. This is exactly the compensation a 0% schema demands.

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 precise verb+resource+effect: download one attachment from a message and write it to the local filesystem. The singling out of 'one attachment' and the write-to-disk outcome clearly separate it from read_email, which merely lists parts.

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?

It establishes the upstream workflow by tying `part` to read_email's `attachments` list and `account` to list_accounts, so an agent knows what must precede this call. It stops short of naming when-not-to-use cases or explicit alternatives, which is the only gap.

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