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

No annotations are provided, so the description carries full burden. It indicates a read operation (listing), but does not disclose other behavioral traits such as side effects, rate limits, or authentication requirements. The description is minimal and lacks depth.

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, clear sentence that effectively communicates the tool's function without unnecessary words. It is front-loaded and efficient.

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 no output schema, the description provides basic information (addresses and message counts) but omits potential details like whether an inbox ID or other metadata is returned. For a simple list tool, it is functional but could be more complete.

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?

With zero parameters, schema coverage is 100%. The description adds no parameter specifics because none exist, so baseline for no parameters is appropriate. It does not need to add meaning beyond 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 it lists inboxes, specifying 'active inboxes' with 'addresses and message counts'. The verb 'list' and resource 'inboxes' are direct, distinguishing it from sibling tools like create_inbox or delete_inbox.

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 implies usage for retrieving inbox information but provides no explicit guidance on when to use this tool versus alternatives like list_messages or list_domains. The distinction is based solely on the resource type, which is adequate but not explicit.

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