apple_mail_save_attachment

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

Annotations already declare a non-readonly, non-destructive, non-idempotent write. The description adds two traits the annotations cannot express: writes are confined to APPLE_MCP_FILE_ROOTS and existing paths are refused (no overwrite). It does not describe permissions, what happens on partial failure, or the response, so it is useful but not rich.

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, zero filler, with the action front-loaded and the refusal constraint immediately after. Nothing can be trimmed without losing meaning.

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 five-parameter write operation with 0% schema coverage and no output schema, the description leaves the agent guessing at how mailId/index/account/mailbox combine and what a valid path looks like. It covers the destination root and overwrite policy but not enough to invoke confidently.

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% across five parameters, so the description carries the full burden. It only obliquely maps to 'path' (existing paths refused) and implies 'index' selects the attachment, saying nothing about mailId, account, or mailbox or the expected path format.

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 gives a specific verb+resource ('Save one attachment to a new file') and constrains the destination ('under APPLE_MCP_FILE_ROOTS'), which separates it from apple_mail_list_attachments. It does not explicitly name that sibling as the way to obtain the index, so sibling differentiation is only implicit.

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 rule 'Existing paths are refused' tells the agent when a call will fail, which is genuine usage guidance, but there is no explicit when-to-use vs alternatives, no mention of using list_attachments to find the index, and no prerequisites stated.

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