How to fetch sovereign bond yields with the Bonds API

Whether you are building a fixed-income dashboard, a macro research tool or just need a reliable source of sovereign bond yields inside your application, the Bonds API gives you a single REST endpoint for yields, yield curves and spreads across 60+ countries. In this post we'll walk through getting an API key, making your first call and plotting a basic yield curve.

What the API gives you

Latest yields for any sovereign maturity (1M to 30Y) with intraday updates.
Historical time series reaching back 5+ years so you can backtest models.
Yield curves pre-aggregated by country and date.
Spreads between any two countries for any tenor.
Sovereign credit ratings from S&P, Moody's and Fitch.

Every plan starts with a 7-day free trial. All endpoints are available on every tier — only rate limits differ.

1. Get your API key

Create a free account at bonds-api.com/register. Once logged in, open Dashboard → API Keys and copy the key. The key is passed as a query parameter on every request:

?api_key=YOUR_API_KEY

2. Your first call: latest US 10Y

Fetch the latest yield on the 10-year US Treasury:

curl "https://www.bonds-api.com/api/v1/yields/latest?country=US&maturity=10Y&api_key=YOUR_API_KEY"

Typical response:

{
  "country_code": "US",
  "maturity": "10Y",
  "yield": 4.217,
  "change_bps": -2.5,
  "date": "2026-04-14T20:00:00Z",
  "source": "US Treasury"
}

3. Build a yield curve in Python

Once you have the key, pulling a full curve is a two-line call:

import requests

API_KEY = "YOUR_API_KEY"
BASE = "https://www.bonds-api.com/api/v1"

r = requests.get(f"{BASE}/yields/curve", params={
    "country": "US",
    "date": "2026-04-14",
    "api_key": API_KEY,
})
curve = r.json()["data"]

for point in curve:
    print(point["maturity"], point["yield"])

Output:

1M   5.31
3M   5.24
6M   5.02
1Y   4.78
2Y   4.42
5Y   4.21
10Y  4.22
30Y  4.47

4. Comparing countries: US vs Germany 10Y spread

The /yields/spread endpoint returns a time series of the yield difference between two sovereigns:

curl "https://www.bonds-api.com/api/v1/yields/spread?base=US&quote=DE&maturity=10Y&from=2026-01-01&to=2026-04-14&api_key=YOUR_API_KEY"

This is useful for monitoring the transatlantic spread, often a leading indicator of EUR/USD moves.

5. Rate limits and pagination

Starter — 1,000 calls/month, 60 req/min
Professional — 10,000 calls/month, 120 req/min
Enterprise — 100,000 calls/month, 300 req/min

Historical endpoints are paginated with page and limit query parameters. Max limit is 1,000 rows per page.

6. Error handling

All errors return a JSON envelope with an error key and an appropriate HTTP status:

{
  "error": "API key is required. Pass it via api_key query parameter."
}

401 — missing or invalid key
402 — quota exhausted
404 — country or maturity not found
429 — rate limit hit

Where to go next

Head to the interactive API documentation at bonds-api.com/docs to try every endpoint live from the browser. If you need coverage, features or SLAs beyond the Enterprise plan, reach out at [email protected].

Happy building.