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

Annotations already declare readOnly/destructive=false; the description adds genuinely useful context beyond them — free, unauthenticated, no payment/key/RPC, and a trust guarantee that the list is folded from the same document /.well-known/x402.json serves so it cannot overclaim. That provenance claim is real behavioral value.

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?

Purpose and return shape are front-loaded in the first two sentences, but the final two sentences — a feedback/complaints solicitation with reply-SLA detail — are pure noise for tool selection and consume roughly a third of the text.

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 no output schema, describing the returned kinds array with its fields compensates well. What's missing is any hint on how to act on the result (e.g., match a scheme/network before x402_verify); the feedback paragraph does not fill that 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?

Zero parameters, so baseline is 4, but the description spends its parameter-level detail on the return shape rather than confirming the no-argument nature. Since no output schema exists the return-shape hint is helpful, but it belongs more to completeness than parameter semantics; netting to a solid mid-high score.

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+resource: the x402 facilitator read contract returning {kinds:[{x402Version, scheme, network, extra?}]}, and identifies it as the tool form of GET /supported. It never names the closely related sibling x402_verify or pay_requirements, so an agent must infer the boundary itself.

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?

Implies usage (discover which schemes/networks this facilitator takes, with no payment or key) but never states explicitly 'call this before x402_verify/pay_send' or any when-not condition. The implicit read-before-act flow is inferable but not spelled out.

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