Quote an x402 endpoint

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

The description adds significant behavioral context beyond the annotations: it makes a request, interprets HTTP 402 challenges, and reports the cheapest acceptable payment. It also explicitly discloses the edge case where a 200 response is treated as 'free' rather than an error, which is valuable and not indicated by the read-only annotation.

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 two sentences, front-loaded with the core purpose, and every sentence adds value. It is concise without being under-specified, covering the request behavior, output fields, and an important edge case.

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, the description adequately explains the return information (amount, asset, network, payee) and handles the special case of 200 responses. It could be more complete by addressing other non-402 statuses or potential errors, but given the tool's simplicity and the annotations, it is largely sufficient.

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 already describes all parameters (url, body, method, headers) with 100% coverage. The description does not add additional parameter-level details beyond the schema, but it does explain the overall output (amount, asset, network, payee), which is return-value information rather than parameter semantics. 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 clearly states the tool's purpose: 'Ask a paid endpoint what it charges, without paying' and details the specific behavior of reading an HTTP 402 challenge and reporting the cheapest payment. This distinguishes it from the sibling ripar_call_endpoint, which actually executes a paid call.

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 clearly communicates the use case: querying a paid endpoint for its price before committing to payment. It implies this should be used instead of ripar_call_endpoint when the user wants a quote only, but it does not explicitly name the alternative or state when not to use it.

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