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

The description goes well beyond the annotations by explaining the deferred flow: nothing is created, no email is sent, the domain is only carried over after the human signs in, and monitoring starts only after TXT ownership verification. It also specifies exact output behavior for signup_url and message. This adds meaningful behavioral context that annotations alone do not provide.

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 first sentence is an excellent front-loaded purpose statement, and the subsequent details about the signup flow and output formatting are necessary for correct agent behavior. The second sentence is long and contains many clauses, but every clause contributes operational information. It is dense rather than bloated, though not maximally concise.

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 one well-documented parameter, an output schema, and annotations covering read-only and idempotent behavior, the description supplies the missing interaction context: who receives the link, how the follow-up flow works, and how the agent must present the output. The explicit instruction to print signup_url verbatim and never sign in on the user's behalf closes the main operational gaps. Nothing essential is left ambiguous.

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 input schema already documents the single parameter 'domain' thoroughly, including accepted formats, punycode normalization, and exclusions. The description adds no additional parameter-level semantics beyond referencing signup_url. With 100% schema description coverage, this meets the baseline but does not exceed it.

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 opening sentence uses a specific verb and object: 'Return a sign-up link to give to the HUMAN who owns a domain, so they can start monitoring it themselves.' This clearly states what the tool does and differentiates it from the sibling checking, generation, and validation tools by emphasizing a self-service handoff. It also explicitly states what the call does not do, which removes ambiguity.

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 gives clear situational guidance: use this tool to hand monitoring start-up to the human domain owner, and never sign in on their behalf. It provides a strong boundary for when this tool is appropriate. However, it does not name sibling alternatives or explicitly state when another tool should be used instead, so it stops short of full when/when-not coverage.

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