List recent messages

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

With no annotations, the description carries the burden of disclosing behavior. It states that messages are listed newest first and defaults to INBOX, implying a read-only operation, but does not mention pagination, whether messages are marked as read, or any authentication/error behavior.

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 a single, front-loaded sentence with no filler. Every word adds value, and it covers the essential behavior, order, and default.

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 simple tool with two optional parameters and no output schema, the description is mostly complete: it states the action, resource, ordering, and default mailbox. It could be improved by briefly explaining the limit parameter and pointing to alternatives, but it is adequate as-is.

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 documents the mailbox parameter and the limit's numeric constraints, but the description adds no extra meaning for 'limit' beyond 'most recent'. Schema description coverage is only 50%, so the description should compensate for the undocumented limit behavior, but it does not.

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 resource ('messages'), clearly distinguishes this from siblings like list_mailboxes and get_message, and adds useful scope: mailbox default INBOX and order newest first.

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 provides clear context for when to use this tool: to list recent messages with a default mailbox. It does not explicitly mention alternatives or when not to use it, but the intended use case is clear enough for most scenarios.

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