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

With no annotations, the description must carry the behavioral burden. It does disclose that the call is free and that it returns a score plus exact fixes, but it omits whether it performs external network fetches against the supplied URL, latency/timeout behavior, and any auth requirements. Useful context, but incomplete for a zero-annotation tool.

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?

Effectively two sentences, front-loaded with the 'FREE' cost signal and the core action before the diagnostic checklist. The parenthetical enumeration is long but each item is a distinct check, so it earns its space.

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 annotations and no output schema, the description covers both what is inspected and what comes back (score and exact fixes), which compensates for the missing output schema. Remaining gaps are environmental details like network behavior and runtime.

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 'url' parameter is documented in the schema as 'The paid endpoint URL'. The description confirms the URL is a paid endpoint but adds no format, scheme, or validation 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?

States a specific verb (check/validate) and resource (x402 paid endpoint configuration) and enumerates the concrete checks it performs (HTTP 402, PAYMENT-REQUIRED v2, XRPL invoiceId/sourceTag, RLUSD issuer, payTo, discovery file). An agent can tell it is a diagnostic rather than a lister, though it never names or contrasts the overlapping sibling xrp_paid_endpoints.

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 'so AI agents can actually pay it' clause implies the pre-flight validation use case, and 'FREE' signals cost, but there is no explicit when-to-use statement, no prerequisites, and no routing to or away from xrp_paid_endpoints. Usage is inferable rather than stated.

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