gmail_add_attachment

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

With no annotations provided, the description bears the full burden of disclosing behavior. It truthfully describes the side effects (only attachments change) and the return value. However, it omits important details such as requirements for the draft to exist, size limits beyond the schema's maxLength, error handling, or permissions, leaving gaps in transparency for an agent.

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 two sentences with no fluff. The first sentence communicates the action, return value, and preservation of other fields; the second succinctly specifies how to pass the attachment. Every sentence is essential and front-loaded, making it easy to scan.

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?

Given the tool's simplicity, the description covers the core functionality well: what it does, what it returns, and the input format. It lacks details on error conditions or prerequisites (e.g., draft must exist), but the presence of an output schema and clear parameter schema mitigate this. It is reasonably complete for a single-purpose attachment tool.

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 rich descriptions for each parameter (e.g., filename, MIME type, base64 data). The tool description adds a brief summary ('Pass the file as attachment (filename + mime_type + base64 data_base64)') but does not significantly enhance understanding beyond the schema. Since schema coverage is high, baseline 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 attaches one file to an existing Gmail draft and returns the updated attachment list. It specifies what changes and what remains unchanged, making the purpose specific and actionable. However, it does not explicitly differentiate from sibling tools like gmail_remove_attachment or gmail_get_attachment, leaving some ambiguity for agents comparing options.

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 implies when to use the tool (when adding an attachment to a draft without altering other parts) and states that only attachments change. It does not provide explicit context on when NOT to use it or mention alternative tools, but the guidance is sufficient for basic scenarios.

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