list_messages

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

With no annotations supplied, the description carries the full burden and does well on the unique parts: it discloses sort order (newest first), the opaque cursor workflow for pagination, and a security warning that subject/sender/preview fields live under an "untrusted" key and must not be followed as instructions. It omits auth/permission requirements and any notion of result volume or rate limits.

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 short sentences, front-loaded with what the tool does and how to page, then the safety caveat. No redundancy and nothing that could be cut without losing information.

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?

For an 8-parameter read tool with no annotations and no output schema, the description covers purpose, paging, and the shape/safety of returned content. A brief pointer to get_message for full message bodies would close the remaining gap.

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 coverage is 75%, so most parameters are already documented. The description adds meaningful context only for folderId (default inbox), nextLink (must come from a previous response), and generic "filters"; from, since, until, top, unreadOnly and hasAttachments gain nothing beyond the schema.

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 messages in a folder"), plus scope details: default inbox, newest-first ordering, filter support, and paging. It does not name or differentiate itself from the sibling search_messages, so an agent must infer which listing tool to pick.

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 implies usage (browse a folder, page with nextLink) but never states when to prefer this over search_messages or when a single-message read (get_message) is more appropriate. The when-to-use context is present but only by implication.

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