messages_list

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It adds useful context: the requirement for alias credentials and the IMAP protocol. However, it does not explicitly state that the operation is read-only, nor does it describe any side effects, performance implications, or return behavior. The credential requirement is a positive disclosure, but the overall behavioral transparency is limited.

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 exceptionally concise: two short sentences that immediately convey the core purpose and a key prerequisite. Every word earns its place, with no filler or redundancy. It is front-loaded with the action and scope, making it easy to scan.

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 tool is complex (16 parameters, nested objects) and has no output schema, yet the description provides only a terse overview. It fails to explain return values, pagination behavior, the lightweight mode, or how the many filters interact. The absence of these details leaves the agent with insufficient information to fully understand the tool's capabilities and response format.

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 input schema already documents all 16 parameters in detail. The description itself adds no parameter-specific semantics beyond the general 'list/search' verb. As per the baseline for high schema coverage, a score of 3 is appropriate; the description neither enhances nor detracts from the schema.

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 clearly states the tool's function: 'List and search messages for an alias (IMAP).' This identifies a specific verb ('list/search'), a resource ('messages'), and a scope ('for an alias'). It distinguishes itself from sibling tools like emails_list by specifying the alias context and IMAP protocol, though it does not explicitly name alternatives.

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 a prerequisite ('Requires alias credentials') but no direct guidance on when to use this tool versus siblings. It does not mention alternatives like emails_list or explain scenarios where this tool is preferred. The usage context is only implied by the phrase 'for an alias,' which is insufficient for choosing among sibling tools.

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