Treasury auction API
One call returns every US Treasury auction result Helious has read: the high yield, the tail against the when-issued yield, the bid to cover against its 12-auction average, the indirect, direct and dealer split, and a strong, in line or weak verdict. Results land within seconds of the Treasury announcement. The first call is free and needs no key.
Bills, notes, bonds, TIPS and FRNs are all covered, each with the CUSIP, the reopening flag and a link to the auction's own page. Every result carries the context a trader needs to judge it: how it compares with the last 12 sales of the same tenor, its percentile, and a dated note such as the weakest bid to cover since a given auction.
Your first call
No account and no key. Paste the line below and run it.
curl "https://api.helious.io/v1/auctions?limit=1"
import requests
r = requests.get("https://api.helious.io/v1/auctions",
params={"tenor": "10-year-note", "limit": 12}, timeout=15)
for a in r.json()["data"]["auctions"]:
print(a["date"], a["high_yield"], a["tail_bps"], a["btc"], a["verdict"])What comes back
Every answer opens with summary, a finished sentence a person or an AI can quote as it is, then source, data and meta.
{
"summary": "The most recent US Treasury auction Helious captured: the 5-Year TIPS on 2026-10-22 stopped at 2.367%, tailing 0.7bp to the when-issued yield, with a bid-to-cover of 2.41 against a 2.47 average of its previous 12 auctions. Indirects took 62.0%, directs 32.4% and dealers 5.5%. Helious desk verdict: IN LINE. That is the weakest bid-to-cover since 2025-04-17 for this tenor.",
"data": {
"auctions": [
{
"date": "2026-10-22",
"tenor": "5-Year",
"type": "TIPS",
"cusip": "91282CRR4",
"reopening": false,
"high_yield": 2.367,
"wi_yield": 2.36,
"tail_bps": 0.7,
"btc": 2.41,
"indirect_pct": 62.0,
"direct_pct": 32.4,
"dealer_pct": 5.5,
"verdict": "IN LINE",
"vs_12m": {
"btc_avg": 2.47,
"indirect_avg": 69.93,
"dealer_avg": 9.19,
"n": 12
},
"pctile": {
"btc": 38,
"n": 16
},
"significance": "the weakest bid-to-cover since 2025-04-17",
"hub_path": "/auctions/5-year-tips"
}
]
},
"meta": {
"tier": "keyless",
"history_days": 1,
"delay_sec": 3600
}
}What each field means
| Field | Meaning |
|---|---|
high_yield | The stop-out yield the auction cleared at, in percent. |
wi_yield | The when-issued yield just before the result, the market's guess at the clearing yield. |
tail_bps | High yield minus when-issued, in basis points. Positive is a tail (weak), negative is a stop-through (strong). |
btc, vs_12m.btc_avg | Bid to cover, and its average over the previous 12 auctions of the same tenor. |
indirect_pct, direct_pct, dealer_pct | Who bought. A high dealer share means the primary dealers had to absorb the supply. |
verdict | STRONG, IN LINE or WEAK, from the tail, the bid to cover and the bidder split together. |
significance | A dated record note, when the result is the highest or lowest of something in a while. |
How it compares
The Treasury's own Fiscal Data API is free and is the official record, so use it for long research history. It publishes the result, not the when-issued yield, so it cannot tell you the tail, and it carries no verdict or 12-auction context. Scrapers that wrap TreasuryDirect have the same gap. Helious reads the result the moment it is announced and returns the tail, the averages and the verdict in the same answer.
What it costs
Every plan sees the same endpoints and the same response shapes, so code written on the free tier keeps working when you upgrade. A data call is 1 credit.
| Plan | Price | History | Freshness | Credits |
|---|---|---|---|---|
| No key | $0 | 1 day | 1 hour behind | 50 credits a month, shared by your network address |
| Free key | $0 | 7 days | 1 hour behind; one call live for 5 credits with fresh=1 | 100 credits a month |
| Starter | $14.99 a month | 12 months | News, prints and auctions live; market prices an hour behind | 1,500 credits a month |
| Pro | $39.99 a month | 24 months | Live, plus the live WebSocket stream | 3,000 credits a month |
| Ultimate | $99 a month | 10 years | Live, commercial use and redistribution | No cap |
In an AI assistant, the same data is the get_auctions tool on the MCP server. For a spreadsheet, a CSV sample of recent rows sits at helious.io/auctions/10-year-note.csv.
Questions
Is there an API for US Treasury auction results?
Yes. GET https://api.helious.io/v1/auctions returns every Treasury auction result with the high yield, the tail against the when-issued yield, the bid to cover against its 12-auction average, the bidder split and a strong, in line or weak verdict. It works with no key at the sample tier.
How fast does the API publish an auction result?
Helious reads each result within seconds of the Treasury announcement. On Starter and above the API serves it live; with no key or a free key it is served an hour behind.
Does the API give the auction tail?
Yes. tail_bps is the high yield minus the when-issued yield in basis points, and tail_desc says it in words. The Treasury's own data does not include the when-issued yield, so it cannot give the tail.
Can I filter by tenor?
Yes. Pass tenor, for example tenor=10-year-note, 30-year-bond or 26-week-bill. Short forms like 10y also work.
How much does the Treasury auction API cost?
The first calls are free with no key. A free account key gets 7 days of history and 100 credits a month. Starter is $14.99 a month for live results and 12 months of history, Pro is $39.99 and Ultimate is $99 with 10 years of history and commercial use.