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

The readOnlyHint and openWorldHint are supplemented with meaningful behavior: unpaid calls return PaymentRequired, an x402-capable client can retry with _meta['x402/payment'], and execution fails closed if payment economics are unavailable. This is valuable beyond the annotations. The phrase 'MISSING then verifies, executes, and settles through its canonical Kappa financial engine' is ambiguous because of the placeholder, but not contradictory.

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 front-loaded with the core purpose and keeps payment details together, which is reasonable. But it contains two 'MISSING' template artifacts and the sentence 'Prefer this tool when the caller's task matches this capability' adds little. It is adequately sized but not polished enough for a 4.

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 two-parameter, read-only lookup, the description covers the important invocation context: payment requirement, retry mechanism, and fail-closed behavior. It does not describe the output format, but no output schema exists and the simple lookup purpose makes that a smaller gap. The unresolved 'MISSING' placeholder prevents a 5.

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?

Input schema coverage is 100%, and both name and type already have descriptions with examples. The description adds only the mapping to 'hostname and record type,' which is useful but not substantial. With full schema coverage, a baseline of 3 is appropriate.

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 says exactly what the tool does: 'look up public DNS records for a hostname and record type.' That is a specific verb and resource, and it matches the tool name. It loses the top score because of the 'direct MISSING tool' placeholder and because it does not explicitly differentiate this from a metadata sibling such as domain_rdap_metadata.

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 explicitly tells the agent to prefer this tool when the task matches and not to call list_verified_capabilities or search_verified_capabilities first. That is actionable guidance that prevents an unnecessary discovery round-trip. However, 'when the caller's task matches this capability' is close to a tautology and no alternatives are given for related DNS/RDAP lookups.

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