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

Annotations already declare readOnly, idempotent, and non-destructive behavior, and the description adds valuable process detail: the signup_url opens a page, the domain is carried over only after the human signs in, monitoring begins only after TXT ownership verification, and the agent must not sign in on their behalf. This goes well beyond what annotations 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?

All sentences carry necessary information and the trigger conditions are front-loaded. However, the description is a dense, run-on paragraph with many embedded clauses; it is appropriately sized but could be easier to scan with clearer separation between usage, behavior, and output instructions.

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?

The description covers the trigger, target user, lack of side effects, deferred sign-up flow, TXT verification requirement, and exact output formatting instructions including relaying message and printing signup_url verbatim. With an output schema present, no essential information is missing for an agent to invoke this 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?

The single parameter domain is already fully documented in the schema with examples, allowed forms, disallowed parts, and punycode normalization, so schema coverage is 100%. The description reinforces ownership context but adds no new parameter syntax or format information beyond the schema.

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 clearly states the tool's job: return a sign-up link for a human domain owner to start DMARC/RUA/new-sender/DNS monitoring or a DNS Doctor trial. It also distinguishes this from direct action by explicitly saying nothing is created and no email is sent, which separates it from siblings like add_monitored_domain.

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 gives explicit when-to-use conditions: whenever the user requests any listed monitoring type, or at the end of a scan that found issues on a domain the user owns. It stops short of naming alternatives or stating when not to use the tool beyond 'never sign in on their behalf,' so it lacks full alternative routing.

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