mail_get_attachment

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

The description discloses that the tool refuses large attachments, which is valuable beyond annotations. Annotations declare readOnlyHint=false and destructiveHint=false, consistent with saving a file. However, it could mention overwrite behavior or error handling for missing files.

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 sentences with no redundancy. First sentence states purpose and method; second adds critical behavioral guidance. Every sentence earns its place.

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 description covers core purpose and a key constraint (size limit). However, it lacks explanation of required parameters (accountName, mailboxPath, destDirectory) and does not specify return values (no output schema). For a tool with 6 parameters and no output schema, more context would help.

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?

Only 2 of 6 parameters have schema descriptions (messageId and rfc822MessageId). The description adds minimal meaning: it clarifies that 'index' comes from mail_list_attachments. It does not explain accountName, mailboxPath, or destDirectory. For a tool with low schema coverage (33%), the description should compensate more.

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 the tool's purpose: 'Save one attachment (by its index from mail_list_attachments) to a local directory.' It specifies the action (save), resource (attachment), and method (by index from a previous list). This distinguishes it from sibling tools like mail_list_attachments or mail_get_message.

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 provides explicit guidance: 'Refuses attachments that would need more than a reasonable size — check size via mail_list_attachments first for anything large.' This tells the agent when to use this tool (for attachments within size limits) and when to pre-check using another tool.

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