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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the safety profile is covered. The description still adds genuinely new context: the data source is live DNS, the call costs $0.01 USDC via x402, and failed calls are not charged. It does not say anything about latency or rate limits.

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?

Very dense but front-loaded: the grade, the weighting, the data source, the safety/cost terms all appear in order with no filler. Slightly run-on across semicolons, but no sentence is wasted.

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?

With one required param, full schema coverage, no output schema and rich annotations, the description still names the return contents (grade, findings, top 3 fixes) and the cost model. Only the A-F grade mapping from the 0-100 score is left unstated.

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' param already documents that an email or URL on the domain also works. The description adds no parameter-level 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?

Specific verb+resource: 'Grade a domain's email security 0-100 (A-F)' with the exact scoring weights (SPF 30, DMARC 40, DKIM 25, MX 5) and output shape. It does not, however, explicitly differentiate itself from the sibling check_domain_email_security or email_fix_plan, whose scope overlaps with the 'top 3 fixes' promise.

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 is only implied by the grading/scoring framing and the stated $0.01 cost; there is no explicit when-to-use or when-not-to-use, and no routing to check_domain_email_security or email_fix_plan for the overlapping jobs.

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