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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, openWorldHint=true. The description adds meaningful behavioral context beyond annotations: it discloses that it reads only public DNS records, sends no email, requires no access, and returns what is missing plus an exact fix compared to a reference study. This is useful transparency, though it stops short of describing output structure (which the output schema covers).

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?

Front-loads the trigger scenarios then the mechanism in a single dense sentence. Slightly verbose with the parenthetical record list and the 7IT comparison, but every element conveys actionable information, not filler.

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?

An output schema exists, so return-value detail is not required. Combined with annotations covering the safety profile and a fully documented parameter, the description provides complete context 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?

Schema coverage is 100% (the single 'url' parameter is documented with an example). The description says it reads a 'domain' but doesn't clarify whether a full URL or just the domain is expected, which the schema already addresses. Baseline 3 is appropriate when the schema does the heavy lifting.

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 (reads/checks) and resource (domain's public DNS records: SPF, DKIM, DMARC, BIMI, MX), and lists the exact records inspected. Clearly distinguishable from siblings like check_app_security, check_accessibility, or check_ai_shopper_readiness, which target different concerns.

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?

Opens with three concrete trigger scenarios: spam delivery, spoofing/phishing protection, and compliance with Gmail/Yahoo/Outlook bulk sender rules. This tells the agent exactly when to invoke this tool over alternatives.

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