list_mailboxes

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds that results include message and unread counts and role classification, which hints at the data shape, but says nothing about ordering, multi-account grouping, or whether unread counts are refreshable.

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?

A single compact sentence with no wasted words, front-loading the resource and then the returned attributes. It is a sentence fragment rather than a complete statement, which slightly weakens readability.

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 zero-parameter, read-only listing tool with an output schema present, the description covers the essentials: what is listed and what fields accompany it. The missing piece is how this list relates to downstream tools in the mail workflow, but nothing required to invoke it is absent.

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 takes zero parameters, so there is no parameter semantics to explain and nothing to compensate for. Baseline 4 applies.

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 names the resource precisely (accounts and their mailboxes) and enumerates the mailbox roles it surfaces, so an agent can tell this is a mailbox-enumeration tool. It lacks any differentiation from siblings like selected_mail or mail_status, and it reads as a noun phrase rather than a verb+resource statement, relying on the name for the action.

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?

There is no when-to-use guidance, no mention of alternatives such as selected_mail or mail_status, and no stated prerequisites. The agent must infer that this is a discovery step used to obtain mailbox identifiers before other mail operations.

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