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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuinely non-structured behavioral context: a paid call at $0.001 native USDC on Base, and that the recursive SPF analysis is bounded (a performance/scope limit) with deterministic suggested fixes rather than open-ended output.

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 tight sentences that front-load the scope of analysis and then the cost. Dense but every clause (checks performed, bounded recursion, deterministic fixes, price) carries information an agent needs.

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?

For a one-parameter diagnostic with no output schema, the description conveys what is analyzed, that recursion is bounded, that fixes are deterministic suggestions, and that the call is paid. It stops short of describing the shape of the returned findings, which is the only notable gap.

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 0% for the single 'domain' parameter, but the parameter name and the tool's framing make its meaning self-evident; no format, subdomain, or TLD constraints are clarified beyond minLength/maxLength. Marginal value over the schema, so a baseline 3 is fair.

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?

The description names concrete resources and checks (SPF/DMARC/DKIM/BIMI diagnostics, CAA/DNSSEC context, recursive SPF resolution), so an agent knows this is a domain email-authentication audit rather than a generic DNS lookup. It never names or contrasts the siblings (domain_preflight, email_preflight, domain_rdap), so differentiation is left to inference.

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?

There is no statement of when to pick this over email_preflight or domain_preflight, nor any prerequisite or exclusion. Usage is only implied by the topic words, which is insufficient given three plausible sibling diagnostics.

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