scdo-agent-plugins

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x402 price quote

x402_quote

Read-only

Fetch HTTP 402 payment requirements from an x402 URL—price, asset, network, and payTo—without paying. Inspect payment terms before sending funds.

Instructions

Fetch the HTTP 402 payment requirements of an x402 URL (price, asset, network, payTo) without paying.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "url": "<url>"
    },
    "name": "x402_quote"
  }
}

Input Schema

Name	Required	Description	Default
`url`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 20, 2026

TDQS

A4/5.0

Behavior3/5

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile and outbound-network nature are known. The description usefully adds that no payment is made, but says nothing about auth requirements, rate limits, or error behavior when the URL is not 402-protected.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

One front-loaded sentence with zero filler; the verb, resource, returned fields, and the key non-side-effect are all packed in efficiently.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description compensates by naming the returned fields (price, asset, network, payTo), which is enough for an agent to use the result. A brief note on failure modes for non-402 URLs would make it complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The single url parameter has 0% schema description coverage, so the description carries the burden; it does clarify that the url is an x402-protected resource to quote. However, it adds no format or validity constraints beyond that bare characterization.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (Fetch) and resource (HTTP 402 payment requirements of an x402 URL), and the phrase 'without paying' immediately separates it from the sibling pay_x402. An agent can tell this is the read-only price-discovery step without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

'without paying' implies the intended use case (inspect requirements before committing funds), which is clear context for choosing this over pay_x402. It stops short of an explicit 'use this before calling pay_x402' routing statement, so it is not a full 5.

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