list_messages

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

With no annotations, the description relies on the verb 'List' to imply a safe read-only operation. It does not disclose ordering, pagination, or side effects like marking messages as read. This is adequate but leaves behavioral traits unstated.

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 one short sentence with no filler or repetition. It is appropriately sized for a simple list operation and every word contributes to the purpose.

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?

Although the schema and output schema cover parameters and return structure, the description lacks any contextual guidance about thread-level scoping versus open messages, or when to use this tool. Given the existence of siblings like list_open_messages and send_message, this minimal description leaves the agent under-informed about the tool's place in the workflow.

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 the baseline is 3. The description adds no additional meaning beyond the schema; it only mentions 'conversation thread' which maps to thread_id. The rich parameter descriptions in the schema do the heavy lifting.

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 uses a specific verb 'List' and identifies the resource 'messages' scoped to 'a conversation thread', which clearly distinguishes it from sibling tools like list_open_messages. However, it does not explicitly contrast with siblings like send_message or mark_message_handled, so it is clear but not overtly differentiating.

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?

No guidance is provided about when to use this tool versus alternatives such as list_open_messages or get_message_event. There are no exclusions, prerequisites, or alternative tool mentions. The description only states what it does, not when or why to use it.

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