Currency Converter API

Fiat and crypto currency converter -- ECB rates for fiat, CoinGecko for crypto. Instant cross-rate lookup. Pay-per-call via x402 (USDC on Base L2) -- no API key, no signup, no rate-limit wall.

Part of the klymax402 marketplace -- 100 x402 micropayment APIs for AI agents, one wallet, USDC on Base.

Quickstart -- MCP

Add to your MCP client config (Claude Desktop, Cursor, ElizaOS, etc.):

{
  "mcpServers": {
    "currency-converter": {
      "url": "https://currency-converter.api.klymax402.com/mcp"
    }
  }
}

Related MCP server: Frankfurter MCP

Quickstart -- HTTP (x402)

curl -X POST "https://currency-converter.api.klymax402.com/api/convert" \
  -H "Content-Type: application/json" \
  -d '{"amount":"1","from":"...","to":"..."}'
# -> 402 Payment Required, with an x402 payment challenge in the response body

Any x402-aware client (@x402/fetch, x402-agent-tools, ATXP) handles the 402 -> sign -> retry cycle automatically.

Tools

finance_convert_currency

Use this when you need to convert between any currencies -- both fiat (USD, EUR, GBP, JPY) and crypto (BTC, ETH, SOL). Returns conversion result in JSON.

Parameters

Returns

• convertedAmount -- the resulting amount in target currency

• exchangeRate -- the rate used for conversion

• from -- source currency code

• to -- target currency code

• amount -- original amount provided

• rateSource -- data source used (ECB for fiat, CoinGecko for crypto)

• timestamp -- when the rate was fetched

Example response:

{"convertedAmount":2815.40,"exchangeRate":0.9218,"from":"USD","to":"EUR","amount":3054.00,"rateSource":"ECB","timestamp":"2026-04-13T12:00:00Z"}

When to use: price conversions across fiat and crypto in a single call. Essential for international pricing, invoice generation, and portfolio valuation in local currency.

Not for: market data or charts (use finance_get_token_price), DeFi swap quotes (use dex_get_swap_quote), wallet balances (use wallet_get_portfolio).

Example agent prompts

• "Convert between any currencies -- both fiat (USD, EUR, GBP, JPY) and crypto (BTC, ETH, SOL)"

Payment

• Protocol: x402 -- HTTP-native pay-per-call, no signup, no API key

• Network: Base L2 (eip155:8453)

• Asset: USDC

• Facilitator: Coinbase CDP (primary), PayAI (fallback)

Part of klymax402

100 x402 micropayment APIs for AI agents -- one wallet, USDC on Base, zero signup.

• Catalog: https://klymax402.com/llms.txt

• Full API reference: https://klymax402.com/llms-full.txt

• Live stats: https://klymax402.com/stats

License

MIT