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

Annotations already cover read-only/idempotent safety, and the description adds substantial behavior beyond them: it discloses live reads from a TXT record and a settings endpoint, states that no Bearer token is required (auth context), and explains the practical distinction between the synchronous signed-redirect flow and the asynchronous OAuth flow. There is no contradiction with 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?

The core purpose is front-loaded in the first two sentences, and each subsequent sentence earns its place: output shape, the flow-type distinction, the template caveat, and auth requirements. It is slightly verbose in the caveat sentence, but the length is justified by genuine protocol nuance.

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 compensates by explicitly stating what it reports (provider and flow type), and it covers auth, data freshness, and the key success-criterion caveat. The one notable gap is the negative case — what is returned when the _domainconnect TXT record is absent — which an agent would have to infer.

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 coverage for the single parameter is 100% — the schema already documents 'domain' with an example. The description only restates the concept of a domain in passing and adds no format, normalization, or validation detail beyond the schema, so the baseline of 3 is appropriate.

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 specifies a concrete verb ('check'), a precise resource (whether a domain's DNS provider implements Domain Connect), and the exact mechanism (reading the _domainconnect TXT record and the provider's settings endpoint). This distinguishes it clearly from sibling tools like txt_record_lookup and dns_provider_lookup, which perform generic DNS lookups without protocol-specific semantics.

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?

The description conveys strong context: it frames the tool as a free public API for assessing Domain Connect support and explicitly warns that provider support is necessary but not sufficient for one-click setup, telling the agent what conclusions it can and cannot draw. However, it never names an alternative tool or states explicit when-not-to-use conditions, leaving sibling trade-offs to inference.

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