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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false), so the bar is lower. The description adds real behavioral value beyond them by disclosing that output varies by auth scope: domains:read keys get verification and mailbox/alias counts, whereas grant-scoped connections only see domains hosting their mailboxes. It stops short of describing pagination or result ordering.

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 tight sentences, zero waste. The core action is front-loaded and the scope-conditional detail follows as qualifying context.

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 output schema, the description usefully previews what the response contains in each scope case (verification, mailbox/alias counts vs. just domain names). That is a strong substitute for a missing output schema; only the return shape for each scope branch could be more explicit.

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, which sets the baseline at 4. The description adds no parameter information, but there is nothing to document, and the schema is trivially complete.

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: 'List the domains this connection can see.' The scoping phrase 'this connection can see' hints at the differentiating factor versus other list_* siblings, but no sibling is named, so an agent must infer that this is the domain-level (not mailbox- or alias-level) listing.

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?

Usage is implied rather than stated: the description explains that results depend on whether the connection holds the domains:read scope, which is useful context for interpreting output. However, it never says when to prefer this over list_mailboxes, list_aliases, or get_account_summary, and gives no explicit exclusions.

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