List message attachments

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

Beyond the annotations (readOnly, idempotent, non-destructive), the description discloses that file contents are never returned and explains why (output budget), plus notes the default limit of 20 per call. This adds valuable behavioral context that the annotations do not cover, with no contradictions.

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 well-structured, front-loading the main purpose and fields, then adding the important caveats about file contents and inline images. It is slightly verbose with the output budget explanation, but every sentence earns its place by conveying essential behavior.

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 list tool with no output schema, the description fully explains the return metadata, pagination default, and a necessary prerequisite. It is complete enough for an agent to call the tool correctly without additional context.

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 both parameters (id and top) with full coverage (100%). The description reinforces the default of 20 per call but does not add new semantic meaning beyond the schema. Baseline of 3 is appropriate when the schema carries the parameter documentation.

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 action ('Lists attachment metadata for one message') and enumerates the specific fields returned (id, name, contentType, size, inline flag, kind). It is unambiguous and distinguishes itself from other mail tools by scoping to a single message's attachments.

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 a clear usage guideline: 'Check hasAttachments on the message first' and warns that inline images count as attachments, which is a practical caveat. It doesn't explicitly mention alternatives or when not to use it, but the prerequisite and the clarification about inline images offer sufficient guidance for typical use.

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