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

Annotations already mark this as non-read-only, non-destructive, and open-world, but the description adds material behavior the annotations cannot: it enables a paid add-on at 5 credits/month, and the nameservers method transfers the domain's DNS to Cloudflare under the provider's account. It also discloses that the call returns setup steps rather than completing setup, which is critical for an agent to know before or after invoking.

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 description is front-loaded with purpose and cost, then method behavior, then the return value, with no filler. It is dense with parenthetical asides, which makes it slightly harder to scan, but every sentence carries information an agent needs.

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?

There is no output schema, so the description correctly specifies that the tool returns setup steps and points to domain_status for verification. It covers cost, method behavior, and a key hostname constraint, leaving only minor gaps such as authentication or plan prerequisites. That is close to complete for a three-parameter mutation tool.

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 is 67%: site is documented in the schema, method has an enum plus a schema description, while hostname has no schema description beyond maxLength. The description compensates by giving hostname examples and the important 'whole domains only, not subdomains' constraint, and it explains the practical trade-off between the two method values better than the schema does. It adds meaning but does not fully restate the site parameter's semantics.

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 states a specific verb and resource ('Connect the owner's own domain') with concrete examples, and it names the related siblings (get_capabilities for available methods, domain_status for verification). An agent can distinguish this from remove_custom_domain and domain_status without opening any schema.

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?

It explains when each method applies (cname = owner adds DNS records; nameservers = DNS moves to Cloudflare) and directs the agent to get_capabilities to see which methods exist. It also states the 'whole domains only, not subdomains' exclusion. It stops short of explicitly saying when not to call this tool at all, so it is clear context rather than a full routing rule.

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