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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds useful behavioral context beyond that: it discloses that the shared domain may appear and that DNS records are returned only for pending custom domains, which is conditional output behavior an agent cannot get from annotations.

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 sentence with zero filler; the resource and its scope are front-loaded before the parenthetical clarifications about shared and pending domains. Every clause carries distinct information.

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 an output schema present, the description needn't document return values, yet it still summarizes what comes back (verification status, needed DNS records). For a no-argument read-only list tool this is essentially complete; only the absence of any routing to sibling list tools keeps it from a 5.

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?

There is a single 'context' parameter whose schema description is fully covered (100%), so the schema does the heavy lifting. The description adds no information about parameters, which is acceptable given the baseline for fully documented, single-parameter schemas.

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 a specific verb ('List') and resource ('the workspace's custom inbound domains'), and clarifies scope by noting the shared {slug}.in.senderkit.email domain is included when used. It is plainly distinguishable from the sibling create/delete domain tools, though it never names them 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?

Usage is implied rather than stated — an agent can infer this is the way to inspect domain verification status and outstanding DNS records. There is no explicit when-to-use/when-not guidance or reference to alternatives such as senderkit_inbound_addresses_list.

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