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

The word 'List' implies a read-only operation, but there are no annotations such as readOnlyHint to confirm this. The description does not disclose pagination behavior, ordering, or what 'stored' means relative to other mail operations, and with no annotations the description carries the full behavioral burden.

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 efficient sentence that states the core purpose immediately. There is no filler or unnecessary detail.

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?

Although the tool is simple, there is no output schema and no annotation coverage, so the description must explain pagination and return shape. It only says 'List stored message ids,' leaving unclear whether the response is a bare array, an object with total counts, or how limit/offset are applied.

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% and limit/offset have empty descriptions. The description never mentions pagination, defaults, maximum limits, or how these parameters affect results, so an agent has essentially no semantic grounding for the parameters.

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 uses a specific verb ('List') and a specific resource ('stored message ids'), with an ownership qualifier ('owned by the caller') that helps distinguish it from broad mail search/inbox tools. However, it does not explicitly contrast with the similar sibling mail_source, so it is clear but not fully differentiated.

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 gives no guidance on when to use this tool versus alternatives like mail_inbox, mail_search, or mail_source. With many mail-related siblings, an agent is left to infer that 'stored message ids' means a listing operation rather than a search or retrieval.

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