x402 agent toolkit: service finder, payment safety, Solana & web tools

by dev.workers.moneytools.x402-pay-precheck

Plan a payment via the MoneyTools Pay Gateway

x402_gateway_plan

Read-onlyIdempotent

Before paying an x402 seller through the non-custodial MoneyTools Pay Gateway: prechecks the seller (valid x402 terms, OFAC-screened payTo) and returns the gateway URL to call, the price and the gateway fee (max(0.5% of price, $0.001), charged from prepaid credits only when the seller answers 2xx). Your own wallet always pays the seller directly; the gateway never holds or signs funds. Then call gatewayUrl with header X-API-Key using any x402 client. Free to try: 20 MCP calls/day per client, no API key or wallet needed (beyond that: prepaid credits via header X-API-Key, see server instructions).

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_gateway_plan"
  }
}

Input Schema

Name	Required	Description	Default
`url`	Yes	seller x402 endpoint you plan to pay
`method`	No	default GET

Output Schema

Name	Required	Description	Default
`decision`	Yes
`precheck`	Yes
`gatewayFee`	No
`gatewayUrl`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 4, 2026

TDQS

A4.1/5.0

Behavior5/5

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

Beyond the annotations (readOnly/idempotent/non-destructive/openWorld), it discloses custody model ('your own wallet always pays the seller directly; the gateway never holds or signs funds'), the exact fee formula and the condition under which a fee is charged (only on a 2xx seller answer, from prepaid credits), and quota/auth rules (20 calls/day free, then X-API-Key). These are exactly the non-obvious facts an agent needs before committing funds.

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

Conciseness4/5

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

It is front-loaded with the precondition ('Before paying...') and each sentence carries operational information rather than padding. It is still a dense single block, with pricing, custody, quota, and next-step details packed together rather than structurally separated.

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

Completeness5/5

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

For a planning/precheck tool it covers everything an agent needs: what is verified, what is returned, who holds funds, cost model, rate limits and auth escalation, and the exact next call. Because an output schema exists, the description is not obligated to detail return values, yet it still names the key returned fields.

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?

Schema coverage is 100%, so the schema already documents both parameters. The description reinforces that 'url' is the seller x402 endpoint being paid, but it says nothing about 'method' (GET default, POST option) or how the planned request's method affects the result. Baseline 3 is appropriate when the schema does the heavy lifting.

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

Purpose4/5

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

The description gives a specific verb and resource: it prechecks an x402 seller (terms validity, OFAC-screened payTo) and returns a gateway URL, price, and fee. The intended step in the payment flow ('Before paying...') is stated. It does not explicitly distinguish itself from close siblings like x402_precheck, x402_validate, or plan_buy, so an agent must infer the boundary.

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?

It clearly states the condition for use ('Before paying an x402 seller through the ... Gateway') and the required follow-up ('Then call gatewayUrl with header X-API-Key using any x402 client'). It never says when not to use it or names an alternative tool for a plain precheck without the gateway, which keeps it below a 5.

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

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