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

With no annotations, the description carries the burden of behavioral disclosure. It reveals that the tool is a read-only inspection operation, shows what data it extracts (terms, issues, payment methods), and discloses the rate limit (100 calls/day). This goes beyond a minimal description, though it could mention error behavior for non-x402 URLs.

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 sentences with zero filler. The first sentence front-loads the user intent and core action, and the second packs high-value specifics (protocol version, networks, amounts, payment options, issues, rate limit) without redundancy. Every clause earns its place.

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?

Despite having no annotations and no output schema, the description effectively explains what the tool returns (terms, issues, payment methods) and its usage context. Minor gaps remain, such as handling of invalid or non-paywall URLs, but for a two-parameter read-only tool the description is sufficient for an agent to call it correctly.

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 input schema already provides 100% description coverage for both parameters. The description adds no new parameter-level details beyond referring to the URL as an 'x402 paywall' and mentioning the address the payment goes to, which slightly contextualizes the URL parameter. This matches the baseline score for high schema coverage.

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 uses a clear verb-resource pair: 'Point it at any x402 paywall and get its terms read for you.' It enumerates specific outputs (protocol version, networks/assets, amount, address, payment options, issues) that make the tool's function unambiguous and distinct from nearby siblings like x402_payment_test or x402_accept_on_arc_how_to.

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 opening question 'How do I pay this URL?' provides immediate context for when to use the tool: when an agent has a URL behind an x402 paywall and needs to discover payment terms. It does not explicitly name alternatives or state when not to use it, but the context is clear enough for an agent to route appropriately.

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