API Documentation

Fast programmatic access to US Treasury yield curve data, auction results, term premia, and FOMC decisions.

Authentication

All endpoints (except /health) require a Bearer token:

Authorization: Bearer ycp_abc123def456...

Generate your token from your Account Dashboard. Tokens use the ycp_ prefix followed by 64 hex characters. Store it securely — it is shown only once.

Base URL

https://www.yieldcurve.pro/api/v1

Rate Limits

Limits reset daily at midnight UTC. Every response includes headers:

• X-RateLimit-Limit — your daily limit for the endpoint
• X-RateLimit-Remaining — requests remaining today

Endpoint	Free	Basic	Pro
curves	10	100	500
levels	10	100	500
slopes	10	100	500
forwards	5	50	250
premia	5	50	250
regimes	5	50	250
auctions	10	100	500
fed	10	100	500

Sandbox Mode

Try any endpoint without an API key using the playground above. Sandbox requests are rate-limited to 10 per day (by IP) and responses are truncated to 5 rows. Sign up for a free account to get full access.

Sandbox base URL: https://www.yieldcurve.pro/api/v1/sandbox

Sandbox responses include "sandbox": true and a "total" field showing the full result count.

Response Format

Success:

{
  "data": [...],
  "count": 42,
  "endpoint": "levels"
}

Error:

{"error": "Human-readable message"}

Status codes: 400 (bad params), 401 (auth), 403 (beta access), 429 (rate limit), 503 (disabled).

Endpoints

GET /health

Health check. No authentication required.

{"status": "ok", "timestamp": "2026-03-01T14:30:00Z"}

GET /curves

Yield curve snapshot for a single date.

Param	Type	Default	Description
date	YYYY-MM-DD	latest	Curve date

{"data": [{"tenor": "3 Mo", "value": 0.0435}, ...], "count": 13, "endpoint": "curves"}

GET /levels

Yield levels time series.

Param	Type	Default	Description
start_date	YYYY-MM-DD	1 year ago	Start of range
end_date	YYYY-MM-DD	today	End of range
tenors	string (multi)	all	Filter to specific tenors

Tenors: 1 Mo, 2 Mo, 3 Mo, 4 Mo, 6 Mo, 1 Yr, 2 Yr, 3 Yr, 5 Yr, 7 Yr, 10 Yr, 20 Yr, 30 Yr

Pass multiple tenors as repeated query params: ?tenors=2+Yr&tenors=10+Yr

GET /slopes

Yield curve spread between two tenors.

Param	Type	Default	Description
start_date	YYYY-MM-DD	1 year ago	Start of range
end_date	YYYY-MM-DD	today	End of range
tenor_long	string	10 Yr	Long-end tenor
tenor_short	string	3 Mo	Short-end tenor

GET /forwards

Par, spot, and forward curves.

Param	Type	Default	Description
date	YYYY-MM-DD	latest	Curve date
horizon	int	12	Forward horizon in months

GET /premia

ACM term premium decomposition.

Param	Type	Default	Description
start_date	YYYY-MM-DD	1 year ago	Start of range
end_date	YYYY-MM-DD	today	End of range
tenors	string (multi)	all	Filter to specific maturities
component	string	both	tp (term premium), rny (risk-neutral yield), or omit for both

Tenors: 1 Yr, 2 Yr, 3 Yr, 5 Yr, 7 Yr, 10 Yr, 20 Yr, 30 Yr

GET /regimes

Yield curve regime classification (Bull/Bear Steep/Flat) with level-slope-twist components.

Param	Type	Default	Description
start_date	YYYY-MM-DD	1 year ago	Start of range
end_date	YYYY-MM-DD	today	End of range
tenor_long	string	10 Yr	Long-end tenor
tenor_short	string	3 Mo	Short-end tenor
lookback	int	251	Rolling window in trading days

GET /auctions

Graded Treasury auction results.

Param	Type	Default	Description
start_date	YYYY-MM-DD	1 year ago	Start of range
end_date	YYYY-MM-DD	today	End of range
tenor	string	10-Year	Auction tenor

Tenors: 4-Week, 8-Week, 13-Week, 17-Week, 26-Week, 52-Week, 2-Year, 3-Year, 5-Year, 7-Year, 10-Year, 20-Year, 30-Year

GET /fed

FOMC rate decisions.

Param	Type	Default	Description
start_date	YYYY-MM-DD	1 year ago	Start of range
end_date	YYYY-MM-DD	today	End of range
changes_only	bool	true	Only show meetings with rate changes

GET /usage

Your current daily usage and limits. No additional parameters.

{
  "tier": "free",
  "data": [
    {"endpoint": "curves", "used": 3, "limit": 10, "remaining": 7},
    ...
  ],
  "endpoint": "usage"
}

Subscription Tiers

Tier	Description
Free	Included with any account
Basic	Higher limits for regular use
Pro	Full access for applications

See current pricing and upgrade from your Account Dashboard.

Example (Python)

import requests

TOKEN = "ycp_..."
BASE = "https://www.yieldcurve.pro/api/v1"

# Get latest yield curve
r = requests.get(f"{BASE}/curves", headers={"Authorization": f"Bearer {TOKEN}"})
print(r.json())

# Get 10Y-2Y spread for 2024
r = requests.get(
    f"{BASE}/slopes",
    params={"start_date": "2024-01-01", "end_date": "2024-12-31",
            "tenor_long": "10 Yr", "tenor_short": "2 Yr"},
    headers={"Authorization": f"Bearer {TOKEN}"},
)
print(r.json())

Example (curl)

curl -H "Authorization: Bearer ycp_..." https://www.yieldcurve.pro/api/v1/curves

curl -H "Authorization: Bearer ycp_..." \
  "https://www.yieldcurve.pro/api/v1/levels?start_date=2024-01-01&tenors=2+Yr&tenors=10+Yr"