messages_list

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

With no annotations, the description carries the burden and does disclose important behavior: headers only, no bodies, and specific header fields (originalTo, authResults) that reveal the real recipient and dkim/dmarc status. It stops short of pagination, ordering, or account-scope details, so not a 5.

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?

Three short sentences, each adding value: what is returned, when to use it, and how to get bodies. Information is front-loaded and no words are wasted.

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?

The description gives a clear mental model and output schema exists, but input parameter semantics are a gap. An agent can start a call, but lacks guidance on query format and pagination behavior, making it adequate but incomplete.

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 the description does not explain query, account, page_token, or max_results. The routing context hints at what data matters, but an agent gets no syntax or semantics for the required query parameter.

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 operation: 'List messages (not threads) with headers only — no bodies.' This distinguishes it from get_thread and get_message, and names the routing-sweep use case. No ambiguity about what the tool returns or omits.

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?

Explicitly says when to use it ('Use for routing sweeps') and points to get_message as the follow-up for bodies 'only where needed'. This gives an agent a clear decision rule against sibling tools.

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