list_attachments

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

With no annotations, the description fully discloses behavior: it returns an array of attachment objects with specific fields, returns an error for nonexistent email IDs, and returns an empty array for emails without attachments. This covers success, error, and edge cases.

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 four concise sentences with no fluff. It fronts the purpose, then gives usage guidance, then describes the return format and edge cases, all in an efficient structure.

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?

Despite having no output schema, the description fully compensates by outlining the return array structure, error behavior, and empty case. It is complete for a one-parameter listing tool, covering all essential aspects.

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 has 100% coverage for the single parameter email_id, including its type and description. The tool description adds context about using it to discover indices, but does not add significant parameter semantics beyond what the schema provides, so the baseline of 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?

The description clearly states the tool's function: 'List attachment metadata for a specific email.' It specifies the resource (attachments), the action (listing metadata), and distinguishes it from the sibling download_attachment by focusing on metadata rather than 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 description explicitly says 'Use this before download_attachment to discover attachment indices and sizes,' providing a direct use case and naming an alternative. This gives clear guidance on when to use this tool versus the download tool.

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