List mailboxes

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

The readOnlyHint annotation already signals safety, and the description adds useful behavioral detail: it returns message counts, unseen counts, special-use roles, and folder writability. This goes beyond the annotation without contradicting it.

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?

Two concise sentences cover purpose, output contents, and a key usage directive with no filler. The essential information is front-loaded and every clause earns its place.

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?

With no output schema, the description fully enumerates what the agent can expect in the response—counts, roles, writability, and a reusable path. It also explains how to apply the result in later calls, making it complete for a parameterless listing tool.

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 there is nothing for the description to explain. The baseline of 4 applies, and the description appropriately focuses on output usage instead of parameter details.

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 lists every folder in the account with counts, special-use roles, and message-holding capability. This distinguishes it from message-focused siblings like list_messages and get_message.

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?

It explicitly instructs that the returned 'path' should be reused verbatim wherever a mailbox is required, giving practical guidance for when to use this tool. It does not explicitly name alternatives, but the zero-parameter scope and mailbox-listing purpose make the use case clear.

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