list_messages

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

There are no annotations, so the description carries the full burden of behavioral disclosure. It communicates that listing is a read operation with pagination, but it does not mention ordering, inclusivity of before/after filters, the shape of the returned results, or any indirect behaviors. This is a meaningful gap for a tool with no annotation support.

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 only two sentences, front-loads the primary action and pagination behavior, and includes no fluff or redundancy. 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?

Given the schema fully describes all parameters and the tool is a straightforward listing operation, the description is mostly adequate. It could be improved by noting the intended pagination flow or expected message chronology, but it is not severely incomplete for an agent to call the tool correctly.

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?

The input schema already covers all six parameters with 100% description coverage, including defaults and date formats. The description adds minimal semantic value beyond reaffirming that accountName and mailboxName scope the request, so a baseline score of 3 is appropriate.

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 and resource ('List messages in a mailbox') and adds the pagination aspect, making the core purpose clear. It does not explicitly distinguish this from sibling tools like search_messages or get_message, so it does not fully earn a 5.

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 tells the agent to provide accountName and mailboxName, which clarifies the required scope for the operation. However, it gives no guidance on when to choose this tool over related alternatives such as search_messages or get_message.

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