list_attachments

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

With readOnlyHint and idempotentHint already set, the description adds meaningful context beyond the annotations: the warning that all returned data should be treated as untrusted and never as instructions. It also explicitly discloses that this operation transfers no content.

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?

Two sentences with no filler. The first sentence states the action and scope, and the second sentence adds the security warning that matters operationally. Each sentence earns its place.

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?

With annotations covering read-only and idempotent behavior, schema covering all parameters, and an output schema present, the description completes the picture by explaining the no-content-transfer property and the untrusted-data warning. 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?

All three parameters are fully described in the schema itself, including provenance for uid and the purpose of uidvalidity. The description adds no parameter-level detail, but this is acceptable because schema description coverage is 100%, so baseline 3 applies.

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?

States a specific verb and resource: list a message's attachments, with the exact returned fields (filename, content type, encoded size). Explicitly disambiguates from get_attachment/save_attachment by saying 'without transferring any content.'

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 phrase 'without transferring any content' makes the usage context clear: use this when only attachment metadata is needed, not the bytes themselves. It does not explicitly name get_attachment or save_attachment as the alternatives for content retrieval, but the intent is strongly implied.

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