list_identities

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

No annotations are provided, so the description must convey behavioral traits. It states the required scope, which is important, but does not detail other behaviors like authentication, rate limits, or error handling. Given the tool's simplicity, this is adequate but leaves some 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 extremely concise with two sentences: one stating the purpose and one specifying the required scope. Every sentence is essential, and there is no verbose or redundant information.

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 tool has no parameters, an output schema (presumably documenting return format), and the description covers the resource and scope, it is complete. The description adequately explains what the tool does and its prerequisite.

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 has no parameters, so the baseline is 4. The description adds value by explaining that the tool lists 'sending identities (email addresses you can send from)', providing context 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 uses a specific verb 'List' and resource 'sending identities', clearly defining the tool's purpose. It distinguishes from sibling tools like list_mailboxes by specifying 'identities (email addresses you can send from)'.

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 clear usage guideline by stating the required scope ('requires the urn:ietf:params:jmap:submission scope'). While it does not explicitly mention when not to use it, the simplicity of the tool and distinct sibling tools make the context clear.

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