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

Annotations only declare readOnlyHint and openWorldHint; the description adds genuinely new facts: the exact pricing model ($0.002 USDC per successful call via x402, with networks listed), that failed calls are free, and that the fingerprint list is community-maintained and verdicts are non-definitive. Those payment and reliability caveats cannot be inferred from annotations or schema.

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?

Two sentences, both front-loaded: the investigative procedure first, then the cost and trust caveat. Nothing is repeated from the schema or annotations, and no filler appears.

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 tool has an output schema, so return values need not be explained, yet the description still tells the agent how to read a verdict and flags the list's community provenance. Combined with the pricing disclosure, an agent has everything needed to call it and interpret results 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?

Only one parameter, and the schema already documents it at 100% coverage with an example ('staging.wordpress.com'). The description's 'For a subdomain' phrasing adds no syntax, format, or validation detail beyond the schema, so this is the baseline adequate score.

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 chain: resolves CNAME, matches against the can-i-take-over-xyz fingerprint list, verifies resolution, and fetches the page for 'unclaimed' text. This is unmistakably a subdomain-takeover check, distinct from sibling DNS tools like security_dns_records or security_dns_propagation, which merely enumerate records.

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?

Usage context is clear (assess a host for takeover exposure) and it sets expectations with 'Verdicts are evidence, not proof; the list is community-maintained,' which tells the agent how to interpret the result. It does not, however, name an alternative tool or state when another check should be preferred, so it stops short of a 5.

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