mailbox_overview

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

With no annotations, the description has to carry the burden, and it does disclose meaningful traits: results are scoped to top-level folders only (not nested), returned sorted largest first, and include mailbox-wide totals. It never explicitly says the operation is read-only or clarifies whether subfolder mail is folded into the top-level counts, which keeps it below a 5.

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 sentences, zero filler, and the output shape is front-loaded ahead of the usage suggestion. Every clause carries information an agent would otherwise have to guess.

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 no-parameter, no-output-schema tool, the description covers what comes back (per-folder message/unread counts plus totals) and the ordering. The one residual ambiguity is 'largest first' — largest by total messages or by unread — which the description does not resolve.

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; the 4 baseline applies. The brief note about scope (top-level folders, totals) is consistent with an argument-free call.

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 exact resource and output shape: 'message and unread counts for every top-level folder, largest first, plus mailbox totals.' The aggregate-count framing naturally separates it from list_folders, list_messages, and the search_* siblings, so an agent can pick it without opening any schema.

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 gives two concrete when-to-use intents: 'size a cleanup' and answer 'how much mail do I have.' That is real routing guidance, but it names no alternative (e.g. sender_stats or find_large_messages for deeper triage) and states no when-not condition, so it falls short of a 5.

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