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

With no annotations at all, the description carries the full burden and does reasonably well: it declares the operation is read-only, enumerates the status states, and discloses the operational constraint of ~50 emails/day per READY box plus last-error and warm-up reputation visibility. Missing auth/permission notes and whether results are paginated or scoped to a sub-account.

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?

Front-loaded with what is returned, then capacity constraint, then usage condition — each clause adds information with no padding. Dense parenthetical style is slightly terse but efficient.

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?

With no annotations and no output schema, the description must convey return content, which it does by naming the status enum, warm-up reputation, and last error. A note on ordering, pagination, or empty-state behavior would close the remaining gap.

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 the schema carries nothing to explain; baseline is 4. The description correctly implies a workspace-scoped, unfiltered listing rather than misrepresenting any 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 resource (the workspace's own connected mailboxes) and enriches it with the status values and per-box fields the agent will see, so it is more than a restatement of the name. It does not explicitly contrast with the close sibling list_sender_emails, leaving a small ambiguity about which mailbox listing to call.

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?

Gives a concrete activation context: used when settings.emailSenderMode=client_owned for classic campaigns and SDR, which tells the agent when this listing is relevant. It stops short of naming alternatives (list_sender_emails, connect_client_mailbox) or stating when not to use it.

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