mail_list_mailboxes

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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true and openWorldHint=false, so the opening "Read-only: never sends, deletes, moves or flags mail" largely restates what structured fields already say. The one genuinely additive detail is the permission scoping ("mailboxes this server is allowed to read"), which tells the agent results may be a subset of the account; return content is also hinted at with "message counts".

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 no filler, safety scope first and the enumeration behavior second. Every clause carries information, and it is short enough to be read in a single glance.

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, closed-world listing tool with no output schema, the description covers the essentials: what is listed, the access scope, and that counts are included. It stops short of describing the mailbox identifier shape or how counts are scoped, but no output schema exists to carry that and the gap is minor.

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 nothing for the description to disambiguate and the baseline is a 4. Nothing in the description misleads about inputs.

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?

States a specific verb and resource ("Lists the mailboxes") plus the scope of that resource ("this server is allowed to read") and what comes back ("message counts"). The resource is self-evidently distinct from the siblings mail_search/mail_read/mail_save_attachment, but the description never explicitly contrasts with them.

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 explicit when-to-use or when-not-to-use guidance, and no sibling is named as an alternative. Usage is only implied: an agent can infer this is the discovery/enumeration step before mail_search or mail_read, but that inference is left to the reader.

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