list_messages

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

Annotations already mark this as read-only, but the description adds meaningful behavioral detail: it returns summaries only, includes a handle for retrieving full messages, and orders results newest first. This goes beyond what annotations or schema provide and helps an agent predict the tool's behavior accurately.

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 two short paragraphs with zero filler. The primary purpose is front-loaded in the first sentence, and the second paragraph adds the essential return-handling detail. Every sentence earns its place.

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 a list-type tool with no required parameters, an output schema, and annotations covering the safety profile, the description is complete. It covers ordering, summary-only behavior, the handle handoff to read_message, and the folder-scoped browsing model. Nothing an agent needs to decide whether to call it or how to use its output is missing.

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 100%, with all five parameters already clearly documented (limit, folder, offset, account, unread_only). The description adds no parameter-specific information, which is acceptable because the schema carries the full burden. Baseline 3 is appropriate here.

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 action ('Browse messages in a folder'), the sorting order ('newest first'), and the response scope ('summaries only (no bodies)'). It also distinguishes itself from read_message by explicitly directing the agent to use read_message for full text, which differentiates it from a key sibling.

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 clear context for when to use this tool (browsing folder summaries) and explicitly routes the agent to read_message for full bodies. It does not explicitly contrast with search_messages, but the browsing vs. searching distinction is implied by the description and sibling names, so the guidance is adequate but not exhaustive.

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