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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is fully covered. The description adds a bit of domain context by calling the addresses 'approved' (verified/allowed) and scoping them to one mailbox, but says nothing about ordering, pagination, or what 'approved' entails.

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?

One short sentence, front-loaded with the verb and resource, with no filler. Every word contributes.

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-only list tool with annotations covering the safety profile, this is minimally adequate. However, with no output schema and no indication of what the returned addresses look like (bare addresses vs. display names, ordering), an agent lacks a complete picture.

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% for the single accountId parameter, so the description must compensate. The phrase 'for one mailbox' does imply that accountId selects the mailbox, which is useful, but it adds no format, origin, or lookup guidance beyond that.

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 (approved From addresses) scoped to one mailbox, which is clearly distinct from siblings like list_mail_accounts or list_mail_folders. It does not explicitly name a sibling to contrast against, but the resource is 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?

There is no when-to-use guidance, no prerequisites, and no mention of alternatives. The purpose (checking which From addresses are authorized) must be inferred entirely from the phrase 'approved From addresses'.

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