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

Annotations already declare a safe, read-only, idempotent, open-world operation, and the description still adds substantial context beyond them: it reads only public DNS and the public registry, sends no message, cannot observe sender reputation or warm-up, and does not promise inbox placement. It also discloses a non-obvious scoring rule (opinion rules affect the score but can never force a not_ready verdict).

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?

Well front-loaded: trigger condition first, then parameters, then return shape and limits. Every sentence carries information, though the long enumeration of return fields overlaps with the existing output schema and could be trimmed.

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?

Given an output schema already exists, the description need not detail returns, yet it adds the verdict vocabulary, the opinion-vs-standard rule semantics, and explicit scope limits (public DNS/registry only, no inbox-placement promise). Nothing needed to call or interpret the tool 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%, so both parameters are already documented in the schema, including normalization of URLs/emails to a domain and the 5-selector cap. The description only restates 'pass the domain and, optionally, up to 5 DKIM selectors' without adding format or behavior detail beyond the schema, 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+resource ('Score a cold-email domain') and frames the exact user question it answers ('is acme-mail.com ready for cold email?'). This clearly separates it from siblings like check_dns_records, check_email_auth, and lookup_domain_registration, which are narrower probes.

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?

Gives an explicit trigger: 'Use this when the user asks whether a new or secondary domain is ready for cold email or outreach.' That is clear when-to-use guidance. It stops short of naming alternatives (e.g., 'for raw DNS lookups use check_dns_records'), so no exclusion routing is provided.

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