download_attachment

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

Beyond the annotations (readOnlyHint=true, destructiveHint=false), the description discloses that the tool returns base64-encoded content and has a 5MB file size limit. This is valuable behavioral information that helps the agent set expectations. It does not mention error handling or auth requirements, but the core behavior is well covered.

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?

The description is extremely concise: two sentences that front-load the purpose, then add usage guidance and return format. Every sentence is informative and no words are wasted. It earns a perfect score for efficiency.

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 tool is simple (4 params, no output schema), and the description covers the essential aspects: what it does, how to prepare (use get_email), what it returns (base64), and a key constraint (≤5MB). The annotations cover safety. For its complexity, the description is fully complete and leaves no significant gaps.

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 input schema already provides 100% parameter coverage, including descriptions for all four parameters. The description adds minimal extra meaning beyond stating 'by filename', which is already captured in the schema's filename description. Since the schema does the heavy lifting, a baseline score of 3 is appropriate.

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 function: 'Download an email attachment by filename.' It uses a specific verb and resource, and it distinguishes itself from sibling tools by focusing on attachment downloads. The description also provides a prerequisite step ('First use get_email'), which clarifies its role in the workflow.

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 usage context by instructing to first use get_email to retrieve attachment filenames. This establishes a recommended sequence and differentiates from get_email itself. However, it does not explicitly mention when not to use this tool or list alternative tools, but given the sibling set, no direct alternative exists.

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