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

With no annotations, the description carries the burden, and it does disclose scope boundaries ("WHOIS + DNS only") and that it flags common misconfigurations. It does not mention rate limits, auth needs, or how failures are reported, but for a read-only audit tool the disclosed behavior is solid.

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?

Three sentences, front-loaded with what is checked, then scope, then routing to alternatives. No filler; every clause carries information an agent needs for selection.

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?

No output schema exists, but the enumeration of checked records (expiry, NS, A/AAAA, MX, SPF, DMARC) effectively communicates what comes back, and sibling routing covers the rest. Nothing needed to call it correctly is missing.

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 description coverage is 100% and the single 'domain' parameter is already documented with format guidance ("Bare domain ... no scheme/path"). The description adds no further parameter meaning beyond what the schema provides, so the baseline 3 applies.

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 (check) and resource (a domain) plus the exact facets covered: WHOIS expiry, nameservers, A/AAAA, MX, SPF, DMARC. It explicitly distinguishes itself from three siblings, so an agent can select it without opening any other 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?

Names three alternatives with the precise condition that selects each: whois_lookup for the WHOIS record alone, email_deliverability_check for DKIM/DNSBL/PTR detail, and domain_report for everything plus SEO. When-to-use and when-not-to-use are both explicit.

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