download_attachment

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

Discloses side effects: file write only when saveTo provided, otherwise read-only. Explains idempotency and security checks. Aligns with annotations and adds context.

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?

Concise and well-structured. Front-loaded action, then prerequisites, then behavior details. No superfluous 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?

Covers all aspects: two modes, prerequisites, security, idempotency, and no output schema needed.

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?

Input schema covers all params with descriptions. Description adds important context: saveTo triggers file write, security constraints, and inline behavior.

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?

Clear verb 'Download' and specific resource 'email attachment by part number'. Distinguishes from siblings like list_attachments and read_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?

Explicitly states to use read_message or list_attachments first to get part numbers. Explains two modes (inline vs saveTo) and when each applies. No explicit exclusions but strong guidance.

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