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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is fully covered by structured data. The description only adds the single-mailbox scoping constraint; it says nothing about whether a not-yet-synced mailbox, auth failure, or rate limit affects the result.

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 short sentence with the scope constraint front and center and no filler. It is efficient, though its brevity reflects under-specification rather than disciplined trimming.

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 simple read tool with full annotation coverage, the description is minimally viable, but it leaves return-shape questions open (flat list vs. folder hierarchy, nesting, unread counts) and gives no hint about the accountId source. No output schema exists to absorb those gaps.

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?

One required parameter (accountId) exists with 0% schema description coverage, so the description must carry the burden and does not: it never names accountId, its expected format, or where the value comes from. The phrase 'one connected mailbox' merely gestures at the concept of an account selector without adding usable semantics.

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 (List) and resource (mail folders) with a scope qualifier ('for one connected mailbox'). That scope distinguishes it from the workspace-wide list_mail_accounts/list_mail_rules siblings only weakly, since it never names an alternative explicitly.

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?

The phrase 'for one connected mailbox' implies the tool works per-account, but there is no when-to-use guidance, no prerequisite (e.g., that a mailbox must be connected via list_mail_accounts first), and no routing to sibling tools that also deal with folders or messages.

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