list_mailboxes

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

With no annotations provided, the description carries the full burden. The verb 'List' inherently conveys a read-only operation, and 'on a given registered domain' states a key prerequisite. However, it does not disclose authentication needs, response shape, pagination, or behavior when the domain is not registered. For a simple list operation this is minimally adequate but leaves gaps.

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, front-loaded sentence with no superfluous words. It communicates the core action and the key constraint efficiently, earning its place without bloat.

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 one required parameter, no output schema, and no annotations, the description plus schema are largely sufficient to select and invoke the tool correctly. The return value (a list of mailboxes) is inferable from the name and verb. Lacking explicit output format and error-case behavior is acceptable for such a straightforward list operation.

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 coverage is 100% for the single domain parameter, so the schema already documents the parameter well. The description adds value by qualifying the domain as 'registered', which is a meaningful constraint not present in the schema. This helps the agent understand the domain must already exist within the system.

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 ('mailboxes') with a scope ('on a given registered domain'). This clearly distinguishes it from siblings like list_domains, create_mailbox, and get_mailbox, making the tool's purpose immediately unambiguous.

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 usage context is implied: call this when you want mailboxes for a specific already-registered domain. However, there is no explicit guidance on when not to use it or which alternatives (e.g., list_domains, get_domain_records) might be more appropriate. The registered-domain qualifier hints at prerequisites but does not spell them out.

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