List attachments

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the agent knows this is a safe read operation. The description adds value by specifying the return fields (part names, sizes, content types) beyond what annotations provide, but does not elaborate on potential edge cases (e.g., messages with no attachments). 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 a single sentence that is concise and front-loaded with the key action and result. It contains no unnecessary words. However, it could be slightly more structured by adding a separate sentence for usage context, but overall it is efficient.

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 that the tool has only one required parameter and an output schema, the description is nearly adequate. It explains what the tool lists but lacks guidance on usage context (e.g., when to retrieve a message's attachments) or parameter clarification. The output schema covers return values, so that gap is mitigated.

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?

Schema description coverage is 0%, meaning the description adds no information about the sole parameter (message_id). The schema only provides type and title. The description should compensate by clarifying the parameter's meaning (e.g., 'ID of the message to list attachments for'), but it does not.

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 ('List a message's attachments with part names, sizes and content types.') clearly specifies the action ('list'), the resource ('attachments of a message'), and the output details ('part names, sizes and content types'). It distinguishes from sibling tools like mail_save_attachment or mail_get.

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 no guidance on when to use this tool versus alternatives (e.g., mail_save_attachment to download). It does not mention prerequisites like needing a message_id or the context in which the tool is useful. The input schema indicates required message_id but no contextual hints.

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