list_mailboxesLists the mailboxes of the account: each one with the people who hold it, the other names that deliver into it and the storage its plan entitles the account to, which every box of it shares. It says who is on a box, never what is in one.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It usefully discloses what data is returned (holders, aliases, storage quota) and explicitly excludes mailbox contents, implying a read-only operation. However, it does not mention permissions, pagination, rate limits, or response ordering, leaving meaningful behavioral gaps for a tool with no annotations.
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, front-loads the core action, and avoids unnecessary repetition. The second sentence earns its place by clarifying the metadata-only scope, though the phrasing 'which every box of it shares' is slightly awkward and could be tighter.
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 parameterless list tool with no output schema, the description explains the key returned fields (holders, aliases, storage entitlement) and explicitly states what is excluded (contents). It is nearly complete for this complexity level, though it could mention ordering or pagination behavior for a listing endpoint.
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 are no parameter semantics to describe. Per the rubric, zero parameters establishes a baseline of 4; the description does not need to compensate for any schema gaps.
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 states a specific verb and resource ('Lists the mailboxes of the account') and details exactly what each returned mailbox includes: holders, aliases, and shared storage entitlement. It also clarifies that it does not expose mailbox contents, which distinguishes it from conversation/message tools. However, it does not explicitly differentiate itself from the sibling poll_mailboxes.
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?
Usage is implied by the scope statement 'says who is on a box, never what is in one,' which suggests the tool is for mailbox metadata rather than message retrieval. But there is no explicit when-to-use guidance, no named alternative such as poll_mailboxes, and no prerequisites or exclusions stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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