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Exchange rates and central bank rates as an API

Euro reference exchange rates for any date since 1999, the ECB key interest rates and US Treasury average rates in one place.

The exchange-rate endpoint returns euro reference rates for any date since 1999 and converts them to any base currency, with an optional amount. These are reference rates published once per working day, not tradable quotes.

The ECB endpoint returns the three key interest rates with their change history. The Treasury endpoint returns monthly average rates by security type for US government debt.

The calls

Each call returns 402 with the price until a payment is attached; an x402 client pays and retries automatically. Calls that fail are not charged. See Get started and the guide for bots and agents for code.

fx-rate-ecb $0.003 per call

European Central Bank euro foreign-exchange reference rates for any date since 1999, converted to any base currency.

curl -i "https://api.ambolt.dev/v1/fx-rate-ecb?base=EUR&symbols=%5B%22DKK%22%2C%22USD%22%5D"
Example response
{
  "base": "EUR",
  "amount": 1,
  "date": "2026-10-02",
  "rates": {
    "DKK": 7.4736,
    "USD": 1.1225
  },
  "source": "Source: European Central Bank euro foreign exchange reference rates, via frankfurter.dev.",
  "fetchedAt": "2026-10-02T21:35:47.668Z"
}

ecb-key-rates $0.003 per call

The three ECB key interest rates with their latest change dates and recent history.

curl -i "https://api.ambolt.dev/v1/ecb-key-rates?history=2"
Example response
{
  "rates": [
    {
      "key": "deposit_facility",
      "label": "Deposit facility rate",
      "latest": {
        "date": "2026-09-16",
        "ratePct": 2.5
      },
      "history": [
        {
          "date": "2026-09-16",
          "ratePct": 2.5
        },
        {
          "date": "2026-06-17",
          "ratePct": 2.25
        }
      ]
    },
    {
      "key": "main_refinancing",
      "label": "Main refinancing operations rate (fixed)",
      "latest": {
        "date": "2026-09-16",
        "ratePct": 2.65
      },
      "history": [
        {
          "date": "2026-09-16",
          "ratePct": 2.65
        },
        {
          "date": "2026-06-17",
          "ratePct": 2.4
        }
      ]
    },
    {
      "key": "marginal_lending",
      "label": "Marginal lending facility rate",
      "latest": {
        "date": "2026-09-16",
        "ratePct": 2.9
      },
      "history": [
        {
          "date": "2026-09-16",
          "ratePct": 2.9
        },
        {
          "date": "2026-06-17",
          "ratePct": 2.65
        }
      ]
    }
  ],
  "source": "Source: European Central Bank, ECB Data Portal (reuse permitted with attribution). Dates are the series' observation dates.",
  "fetchedAt": "2026-10-02T21:35:42.198Z"
}

us-treasury-rates $0.003 per call

Monthly average interest rates on US Treasury marketable securities (bills, notes, bonds, TIPS, FRNs) Latest months first.

curl -i "https://api.ambolt.dev/v1/us-treasury-rates?months=2"
Example response
{
  "months": [
    {
      "recordDate": "2026-08-31",
      "rates": [
        {
          "security": "Treasury Bills",
          "ratePct": 3.788
        },
        {
          "security": "Treasury Notes",
          "ratePct": 3.345
        },
        {
          "security": "Treasury Bonds",
          "ratePct": 3.453
        }
      ]
    },
    {
      "recordDate": "2026-07-31",
      "rates": [
        {
          "security": "Treasury Bills",
          "ratePct": 3.758
        },
        {
          "security": "Treasury Notes",
          "ratePct": 3.309
        },
        {
          "security": "Treasury Bonds",
          "ratePct": 3.442
        }
      ]
    }
  ],
  "source": "Source: U.S. Department of the Treasury, Fiscal Data (public domain). Average interest rates are month-end averages on outstanding securities, not market yields.",
  "fetchedAt": "2026-10-02T21:36:03.043Z"
}

Questions

What happens on weekends?

You get the last working day's rate.

Can I use these for trading?

No. They are reference rates, not live quotes, and nothing here is advice.

Use it from an AI agent

Every call is also an MCP tool: add https://api.ambolt.dev/mcp to your agent's server list.