download_attachment

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

With no annotations, the description carries the behavioral burden. It clearly discloses the disk-write side effect, the configured destination directory, and the return value. Minor omissions like overwrite behavior and permission requirements exist, but the core behavioral traits are transparently stated.

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?

Three concise sentences front-load the primary action and destination, then provide identification rules and the return value. There is no repetition of schema details or wasted wording.

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 straightforward four-parameter tool with no output schema, the description covers what the tool does, how to identify the target attachment, the special single-attachment case, and the returned saved file path. The schema handles the remaining parameter details, so nothing essential 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?

The schema already describes all four parameters at 100% coverage. The description adds valuable semantic relationships: filename and index are alternatives, and neither is needed for a single-attachment message. This goes beyond the schema's isolated parameter descriptions.

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 uses a specific verb ('Save') with a clear resource ('an attachment from a message to disk'), making the tool's function immediately obvious. It also distinguishes itself from the sibling mail-handling tools by focusing on attachment persistence rather than message composition or search.

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 gives clear practical context: identify the attachment by filename or 0-based index from get_message, and omit both when there is only one attachment. It does not explicitly name alternatives or exclusions, but the workflow guidance makes appropriate use clear.

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