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

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

Currency converter

currency_convert

Read-onlyIdempotent

Convert fiat amounts with daily ECB reference rates (Source: ECB statistics, via frankfurter.dev). Only currencies published by the ECB are supported. Not tradable quotes. Free: 10 calls/day; then $0.001/call via x402 (MCP params._meta["x402/payment"] or HTTP) or X-API-Key credits. [served by tools.moneytools.dev]

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": {
      "from": "<from>",
      "to": "<to>"
    },
    "name": "currency_convert"
  }
}

Input Schema

Name	Required	Description
`to`	Yes	one or more ECB-published codes, comma list
`from`	Yes	ISO 4217 code (ECB-published)
`amount`	No	default 1

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedNov 10, 2026

changedInput schema / properties / from / description

Previous value: -"ISO 4217 code"New value: +"ISO 4217 code (ECB-published)"

changedInput schema / properties / to / description

Previous value: -"one or more codes, comma list"New value: +"one or more ECB-published codes, comma list"

changedInput schema / properties / to / examples

Previous value: -[
-  "TWD,EUR"
-]New value: +[
+  "EUR,GBP"
+]

First observedNov 4, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description goes beyond that with genuinely operational context: daily (not real-time) ECB rates, non-tradable reference data, a 10 calls/day free tier, and the two payment/auth paths (x402 via params._meta or HTTP, or X-API-Key credits). It stops short of stating rounding/precision or failure behavior for unsupported codes.

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?

Four short sentences, front-loaded with purpose and followed by scope, data caveat, and cost/auth details, so an agent can stop reading early if unconstrained. The trailing "[served by tools.moneytools.dev]" is low-value boilerplate but minimal.

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?

An output schema exists, so return-value explanation is rightly omitted, and annotations cover the safety profile. The description supplies the remaining operational essentials (source, freshness, currency eligibility, rate limits, auth). Only edge-case behavior for invalid or unpublished codes is left unspecified.

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 description coverage is 100% and each parameter carries a description plus examples, so the schema already does the heavy lifting. The description adds only indirect meaning ("amounts", ECB-published codes) and does not explain the multi-target comma list result shape or default behavior beyond what the schema states.

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 and resource ("Convert fiat amounts"), names the rate source (daily ECB reference rates via frankfurter.dev), and bounds the domain with "Only currencies published by the ECB are supported." This clearly separates it from the other *_convert siblings such as unit_convert or color_convert, which deal with non-fiat units.

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

Usage Guidelines3/5

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

"Not tradable quotes" tells the agent when the output is inappropriate for trading use, and the ECB-only restriction defines when it can be used at all. However, there is no explicit routing guidance to an alternative (e.g., a live-rate or crypto-price tool) and no stated prerequisites, so usage is only implied rather than directed.

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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