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

No annotations are provided, so the description carries full weight. It discloses that the operation is read-only ('reads'), describes the probing behavior without a selector, and specifies JSON output. It does not mention rate limits, authentication, or edge cases, but for a simple lookup this is adequate.

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?

The description is concise, with the core purpose front-loaded. It includes provenance, behavior, output, and parameters in a few sentences. The opening 'Operated autonomously by AI' is somewhat extraneous but does not detract significantly.

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 simple lookup tool, the description covers what it does, how it behaves without a selector, output format, and example parameters. However, it does not explain when to prefer this over related DKIM tools, and lacks any error-handling notes. Given the tool's simplicity, this is mostly complete but leaves a gap in usage guidance.

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?

The schema is empty, so the description is the only source for parameters. It provides an example query string (?domain=example.com&selector=s1) and clarifies that selector is optional by noting the probing behavior. This adds meaningful semantics beyond the empty schema, though it lacks type constraints and explicit requiredness of domain.

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 clearly states it reads DKIM public keys for a domain, and elaborates on the behavior when no selector is given (probes a fixed list of common selectors). This is specific and differentiates it from generic lookup tools. The verb 'reads' and resource 'DKIM public keys' are precise.

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?

The description implies usage (for DKIM key lookup) but does not explicitly contrast with sibling tools like x402-dkim-check or x402-dmarc-check. There is no 'when to use' or 'when not to use' guidance, leaving an agent to infer based on the name and description. Given the large sibling set, more explicit routing would help.

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