List mailboxes

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, covering safety. The description adds transparency about the exact output contents (counts, roles, hold-messages capability), and nothing contradicts the annotation metadata.

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 two sentences: the first states the function and output, the second gives a direct, actionable instruction. No unnecessary words or redundant details are present.

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 that an output schema exists, the description does not need to enumerate return fields. It sufficiently explains the nature of the returned data and provides the key usage hint about the path, making the tool's full behavior clear.

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 tool has zero parameters, so there is no parameter ambiguity or need for additional description. Schema coverage is 100% by definition, and the description correctly omits any parameter references.

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 action (lists), the resource (every folder in the account), and the specific data returned (message counts, unseen counts, special-use roles, and whether it can hold messages). It is easily distinguishable from sibling tools that list messages or retrieve individual messages.

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 includes practical guidance on using the returned 'path' verbatim for other mailbox-taking tools, which is a direct usage instruction. It does not explicitly name alternatives, but the distinct resource (mailboxes vs. messages) makes the appropriate context clear.

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