upload_attachment

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

No annotations are provided, so the description carries the full burden. It states that the tool uploads a file and returns an attachment_id, but it does not disclose any side effects, auth requirements, rate limits, or file size restrictions. The description is not misleading but adds only the basic behavioral expectation.

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 concise and well-structured, with a one-sentence summary, a clear note about the return value, and an Args block with three lines of parameter guidance. Every sentence serves a purpose and nothing is redundant.

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 simple 3-parameter tool with an output schema, the description provides the essential context: what the tool does, what input is expected, and what the output is used for. It lacks but does not desperately require details like size limits or retention policies, so it is reasonably complete.

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 description adds valuable meaning beyond the schema's bare property titles: it explains that 'content' must be Base64-encoded and provides concrete examples for 'filename' and 'mime_type'. This compensates for the 0% schema description coverage, though it does not mention limits or format edge cases.

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 verb 'Upload' and the resource 'a file for use when sending emails', which distinguishes it from siblings like 'send_email' and 'get_attachment_url'. It also specifies the return value (attachment_id) and its purpose, making the tool's role obvious.

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 clear context that this tool is for uploading files to be used with 'send_email' via the returned attachment_id. It does not explicitly mention when not to use it or suggest alternatives, but the intended usage is evident from the wording and the sibling context.

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