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

Annotations already mark the call as idempotent and non-destructive, and the description adds concrete behavioral detail: it returns the ownership-check TXT record, does not apply anything to DNS, requires human publication and approval, and instructs the agent to print record strings exactly as returned. This goes well beyond the annotation flags and prevents an agent from assuming it can or should modify DNS directly. No contradiction with readOnlyHint=false or idempotentHint=true.

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?

Four sentences cover the core action, return contents, idempotency, and the critical human-approval/exact-printing constraints, with the main verb and resource front-loaded in the first sentence. No filler or repetition of schema fields. Every sentence adds operational value.

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?

For a one-parameter tool with an output schema, the description covers the required preconditions (linked account, owned domain), return contents, idempotent behavior, and the essential constraint that no DNS changes are applied by the tool. It also includes the exact-output and approval instructions that an agent needs to act safely. The only minor omission is an explicit 'when not to use', but the schema and sibling context make this manageable.

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 schema already provides 100% coverage of the single required domain parameter, including ownership and re-add semantics, so the description does not need to add much. The description reinforces that the domain belongs to the signed-in user's account and that re-adding returns the existing domain, matching the schema. Baseline 3 is appropriate because the schema carries the parameter meaning.

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 opens with a specific verb and resource: 'Add a domain to the signed-in user's DNS Doctor monitoring' and enumerates the exact return payload (TXT record, hosting location, guide link, optional apply URL). This makes it distinct from sibling tools like check_domain_verification or get_domain_records, which operate on already-monitored domains. No ambiguity about what the tool does.

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 clearly frames when the tool is used — when a domain needs to be added to the signed-in user's monitoring — and the schema's domain parameter further distinguishes it from check_domain_verification and get_domain_records by noting those require an already-monitored domain. It does not explicitly name alternatives or state 'use X instead', but the context is sufficiently clear. The idempotent re-add behavior also tells agents they can safely call it even if the domain is already monitored.

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