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

Annotations cover the safety profile (readOnlyHint=false, idempotentHint=true, openWorldHint=true), so the bar is lower. The description still adds real value beyond them: it discloses the external DNS lookup nature and the non-failing contract ('returns the current domain status instead of failing'), which an agent would otherwise not know.

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 with the primary behavior front-loaded and the failure-avoidance nuance immediately after. No filler or redundant restatement of the tool name.

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's explanation of the degraded return (status instead of an error) is exactly the right completion. It falls short on workflow context — permission requirements, expected propagation timing/re-polling, and its relationship to connect_custom_domain and get_custom_domain_status.

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% and the description says nothing about customDomainId, despite it being the sole required input. The uuid format/pattern in the schema specifies the type but not where to obtain the identifier, and the description does not compensate for that gap.

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+resource ('Check DNS... and activate') with a clear scope restricted to pending or stale custom domains. It is distinguishable from get_custom_domain_status by the activation behavior, though it never names that sibling explicitly to sharpen the contrast.

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?

'Pending or stale custom domain' implies the operating condition, and 'when records have propagated' hints at prerequisites. However, it never states when to prefer this over get_custom_domain_status or whether connect_custom_domain must run first, leaving the agent to infer the workflow.

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