mail_list_messages

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

Beyond the readOnly/idempotent annotations, it discloses non-obvious behavior: pagination cursors are stable and scoped to account/folder/UIDVALIDITY, empty pages must still be followed, and oversized results (>64 KiB) are written to a private JSON file with a completeResultFile pointer. That is meaningful disclosure the annotations cannot convey.

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?

Four tight sentences, front-loaded with the core action and scope before pagination and truncation details. Every sentence carries distinct information, though the density borders on terse for the pagination rule.

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?

No output schema exists, yet the description covers the return shape at a high level (metadata plus pagination, plus the completeResultFile fallback) and the full pagination procedure, so an agent can call it correctly. It stops short of naming the returned metadata fields or the concrete page-size limit.

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?

With 0% schema description coverage, the description does the heavy lifting: it explains cursor continuation and its stability guarantees, that folder scopes the listing to a single folder, and account scoping. pageSize is left entirely unexplained, which is the one real gap.

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 gives a specific verb and resource ('List messages'), plus concrete ordering and scope ('newest UID first in one folder', 'entire retained history with no date cutoff'). It implicitly contrasts with a filtered search tool but never names a sibling like mail_search_messages or mail_get_messages, so differentiation requires inference.

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?

It gives clear operational guidance: read folders first, repeat per folder to cover the account, and continue nextCursor even when a page is empty. That is strong how-to-use context, though it never states when to prefer this over mail_search_messages or mail_get_messages.

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