list_mailboxes

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

With no annotations, the description carries the behavioral burden. It does well by disclosing that return is organized into Labels/ and Folders/ groups and includes message/unread counts, which is beyond what the name alone conveys. The read-only nature is reasonably implied by 'List.'

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 short sentences, with the core action front-loaded and the second sentence adding only the non-obvious folder-vs-label grouping behavior. There is no redundant wording.

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?

The tool is simple, has only one optional parameter, and has an output schema, so the description does not need to detail return fields. It covers the key behavioral nuance about label/folder grouping, and only the account parameter semantics and alternative-tool routing are left under-specified.

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?

Schema description coverage is 0%, and the description adds no meaning to the 'account' parameter. The schema provides only a name and default value, which leaves ambiguity about what 'account' refers to and how to select a non-default account.

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 and resource: 'List folders with message and unread counts.' It also distinguishes itself from label-specific tools by explaining how ProtonMail labels appear under Labels/ and custom folders under Folders/, making its scope unambiguous.

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?

No guidance is given about when to use this tool versus siblings like list_labels or list_accounts. The description implies it is for folder-level listing but does not state exclusions or alternatives, so the agent must infer the appropriate context.

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