gmail_list_threads

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

Annotations already declare readOnly, idempotent, non-destructive, openWorld. The description adds real context beyond them: results are thread metadata rather than full message bodies, and paging is supported via tokens. It does not mention how the extra API cost of include_from behaves, but that detail lives in the schema.

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 earning its place, with the core purpose and the "metadata only" constraint front-loaded. No filler.

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?

With no output schema, the description carries the burden of explaining what comes back, and "thread metadata only" is vague about which fields (id, snippet, labels, date) are present. The safety profile and paging are adequately covered elsewhere, but the return-shape gap keeps this at minimum viable.

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%, so every parameter including the Gmail query syntax example and the include_from cost note is already documented. The description adds no parameter semantics beyond echoing token-based paging, so baseline 3 applies.

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 ("Searches Gmail ... returns thread metadata only") and the "metadata only" qualifier implicitly separates it from message-level tools like gmail_search_messages. It stops short of naming a sibling directly, so it is clear but not maximally 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?

"Supports page tokens to walk large result sets" gives implied usage for pagination, and "Read-only" frames safe context. But there is no explicit guidance on when to pick this over gmail_search_messages, gmail_semantic_search, or gmail_get_thread_summary.

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