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

Annotations already provide idempotentHint and non-destructive context, but the description adds valuable behavior: start returns a TXT record, check verifies it, failed DNS lookup returns an error rather than 'not owned', and verification gates list_domains. These are meaningful behavioral details beyond the 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?

Every sentence earns its place: the trigger condition, the core mechanism, the action distinction, the list_domains dependency, and the error semantics. It is front-loaded with the most important usage guidance and avoids filler.

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 two-parameter tool with no output schema, the description covers the necessary workflow, return behaviors, and a key error case. It also connects the tool to the broader system state via list_domains, making it complete enough for an agent to invoke correctly.

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 only 50%, but the description compensates by explaining what each action does: 'start' returns the TXT record and 'check' verifies it. The domain parameter is self-evident from context. The description adds real meaning to the action enum beyond the schema's default note.

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 and resource: proving domain ownership via a DNS TXT challenge, with two explicit actions. It also distinguishes itself by explaining that verification is required before a domain appears in list_domains, differentiating it from sibling domain-related tools.

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?

Explicitly says to use it when the user claims a domain is theirs and the agent is about to act on that claim. It also provides workflow guidance (start then check) and states the prerequisite relationship to list_domains, which serves as clear when-to-use context.

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