mail_save_attachment

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

Adds substantial context beyond the annotations: never overwrites, limited file types, writes to the user's local folder, requires user approval, and carries a prompt-injection warning about untrusted email content. The opening "Read-only" claim is explicitly scoped to mail actions ("never sends, deletes, moves or flags mail") and is immediately reconciled with "This writes a file to the user's local folder", so it does not conflict with readOnlyHint=false.

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 tight sentences with no filler, but the safety preamble and injection warning lead, pushing the actual purpose ("Saves one attachment...") into the third sentence. Front-loading what the tool does before its safety posture would be stronger.

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?

Covers the facts an agent most needs for a filesystem-writing tool: approval requirement, no-overwrite guarantee, and file-type limits. With no output schema, it could still say what a successful save returns (e.g. the saved path) and how failures such as a blocked file type surface.

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 has to carry the load. It loosely maps to three of the four parameters (message/ref, attachment/attachmentIndex, destination folder/destinationDir) but never explains formats, that attachmentIndex is 0-based, or the purpose of the optional filename parameter.

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: "Saves one attachment into an allowed folder", with the scope narrowed to a single attachment. This is unmistakably different from the sibling tools (mail_list_mailboxes, mail_search, mail_read), none of which persist files to disk.

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?

Gives a concrete usage precondition (confirm message, attachment and destination folder with the user; the user must approve before saving) rather than leaving the workflow implicit. It does not name the sibling tools or state when-not-to-use (e.g. use mail_read to inspect a message instead), which keeps it short of a 5.

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