Keppet Open Data

Free, daily, USD-anchored open data for the world's currencies, metals, crypto, reference rates and sovereign yield curves. Official keyless feeds, normalised to one envelope and committed as static JSON — served globally by jsDelivr straight from this repo. No server, no database, no API key, no rate limits.

Discovery — one URL to find everything

An agent fetches a single file to learn the whole catalog: every dataset, its CDN path, unit, cadence, count and sources.

https://cdn.jsdelivr.net/gh/forge-arcana/kod-data@main/catalog.json

For LLM agents there is also an llms.txt — the same catalog as prose an agent ingests in one read, including the USD-anchor rule:

https://cdn.jsdelivr.net/gh/forge-arcana/kod-data@main/llms.txt

{
  "name": "Keppet Open Data",
  "anchor": "USD",
  "conversion": "value_of_X_in_Y = usd_value(X) / usd_value(Y); fiat usd_value=1/rate, price-domains usd_value=price",
  "cdn": "https://cdn.jsdelivr.net/gh/forge-arcana/kod-data@main",
  "datasets": [
    { "id": "fx", "latest": "fx/v1/usd.min.json", "unit": "per_usd", "count": 158, "...": 0 },
    { "id": "metals", "latest": "metals/v1/latest.min.json", "unit": "usd_per_oz", "count": 4, "...": 0 }
  ]
}

Endpoints

Every dataset has a latest (minified + pretty) plus dated snapshots for any past day. Resolve a path from catalog.json or use the patterns directly:

https://cdn.jsdelivr.net/gh/forge-arcana/kod-data@main/fx/v1/usd.min.json         # FX — every world currency
https://cdn.jsdelivr.net/gh/forge-arcana/kod-data@main/metals/v1/latest.min.json  # precious metals
https://cdn.jsdelivr.net/gh/forge-arcana/kod-data@main/crypto/v1/latest.min.json  # cryptocurrencies
https://cdn.jsdelivr.net/gh/forge-arcana/kod-data@main/rates/v1/latest.min.json   # reference & policy rates
https://cdn.jsdelivr.net/gh/forge-arcana/kod-data@main/yields/v1/latest.min.json  # sovereign yield curves

Variants for each dataset:

.../fx/v1/usd.json            # pretty-printed
.../fx/v1/2026-06-26.min.json # any past day (dated snapshot)

Raw GitHub works as an uncached fallback with lower limits:

https://raw.githubusercontent.com/forge-arcana/kod-data/main/fx/v1/usd.min.json

The canonical envelope

Every dataset shares one shape, so a consumer learns it once:

{
  "$schema": ".../schema/<domain>.schema.json",
  "dataset": "fx",
  "base": "USD",
  "date": "2026-06-26",
  "updated": "2026-06-28T17:25:10.343Z",
  "sources": ["un", "bis", "ecb"],
  "...": "domain payload"
}

date is the feed's effective date, not build time (updated). base is always USD.

Formats per domain

fx — rates[CODE] is units of CODE per 1 USD; USD is the anchor and always 1.

{ "dataset": "fx", "base": "USD", "date": "2026-06-26",
  "rates": { "EUR": 0.877116, "GBP": 0.756539, "JPY": 161.6525, "XAU": 0.000244, "USD": 1 } }

metals — USD price of one troy ounce (base carries unit: "troy_ounce").

{ "dataset": "metals", "base": "USD", "unit": "troy_ounce", "date": "2026-06-26",
  "prices": { "XAU": 4082.025, "XAG": 58.804, "XPT": 1631.12, "XPD": 1209.495 } }

crypto — USD price of one coin.

{ "dataset": "crypto", "base": "USD", "date": "2026-06-28", "count": 96,
  "prices": { "BTC": 59574, "ETH": 1567.82, "BNB": 550.49, "ADA": 0.143036 } }

rates — overnight reference rates and central-bank policy rates, in percent, each with its own effective date and source.

{ "dataset": "rates", "date": "2026-06-28",
  "reference": { "SOFR": { "percent": 3.64, "date": "2026-06-25", "source": "nyfed" },
                 "ESTR": { "percent": 2.183, "date": "2026-06-25", "source": "ecb" } },
  "policy": { "BR": { "percent": 14.25, "date": "2026-06-23" },
              "CA": { "percent": 2.25, "date": "2026-06-22" } } }

yields — sovereign yield curve by tenor, in percent.

{ "dataset": "yields", "base": "USD", "date": "2026-06-26",
  "curves": { "US": { "unit": "percent",
    "tenors": { "3M": 3.83, "2Y": 4.07, "10Y": 4.38, "30Y": 4.87 } } } }

Universal conversion

Because every value is anchored to USD, any cross-domain pair reduces to one formula:

value_of_X_in_Y = usd_value(X) / usd_value(Y)

where the per-domain usd_value is:

• fiat (fx): usd_value = 1 / rates[X] — rates[X] is units of X per USD.
• price domains (metals, crypto): usd_value = price — USD price of one unit.

Worked example — gold in EUR

One ounce of gold priced in euros, using metals.prices.XAU and fx.rates.EUR:

usd_value(XAU) = 4082.025          # USD per ounce
usd_value(EUR) = 1 / 0.877116      # USD per euro
XAU_in_EUR = 4082.025 / (1 / 0.877116) = 4082.025 * 0.877116 ≈ 3580.4 EUR/oz

Worked example — BTC in JPY

usd_value(BTC) = 59574             # USD per coin
usd_value(JPY) = 1 / 161.6525      # USD per yen
BTC_in_JPY = 59574 * 161.6525 ≈ 9,630,500 JPY

The general FX re-anchor (currency X in base B) is the same rule: rate of X in B = rates[B] / rates[X]. Metals are also folded into FX as currencies (rates[XAU] = 1 / usd_price), so gold-in-yen falls straight out of rates[B] / rates[X] with no special case.

Agents & MCP

The data is agent-ready with zero integration: any LLM with a fetch tool can read llms.txt (or catalog.json) and consume every feed directly — the files are self-describing, including the USD-anchor formula.

For a typed interface, the keppet-mcp server wraps the feeds as Model Context Protocol tools (list_datasets, convert, get_fx, get_metals, get_crypto, get_rates, get_yield_curve). It is zero-dependency and keyless — a thin wrapper over this CDN — and convert does the cross-domain USD-anchor math for you:

{
  "mcpServers": {
    "keppet": { "command": "npx", "args": ["-y", "keppet-mcp"] }
  }
}

Then an agent can ask convert(from: "BTC", to: "JPY") or convert(from: "XAU", to: "EUR") and get a number back. See mcp/README.md.

Sources

All data comes only from official institutions — no third-party aggregators, no scraping where an official table exists — and every feed is keyless.

Domain	Source	Institution
fx	un	UN Operational Rates of Exchange — ~151 currencies, base layer
fx	bis	Bank for International Settlements — ~60 currencies, daily
fx	ecb	European Central Bank — euro reference rates, freshest majors
fx, metals	lbma	LBMA — London precious-metal benchmarks
metals	swissquote	Swissquote public metals feed
crypto	coingecko	CoinGecko public price API
rates	nyfed	Federal Reserve Bank of New York — SOFR
rates	ecb	ECB — €STR
rates	bis	BIS — central-bank policy rates
yields	us-treasury	U.S. Treasury — daily par yield curve

payload.sources records which feeds actually contributed to each build. FX layers its sources widest-first (UN → BIS → ECB): every currency is present, the majors are freshest, exotics fall back to the UN's monthly figure.

Cadence

A scheduled GitHub Action rebuilds daily and commits only when values change. The upstreams publish about once per working day, so most runs are no-ops. If a feed fails or coverage drops below a sanity floor, the builder keeps the last committed file — a bad upstream day degrades to yesterday's data, never to broken output. For genuine intraday data a paid market feed would be required — out of scope for a daily reference API.

History & archive

The public CDN serves the hot tier: current values plus a rolling 90-day window of dated JSON snapshots (<domain>/v1/<date>.min.json) per domain. Git history of any path is that window's revision history and the last-good fallback.

The deep history — the full USD-anchored, tidy long-form observation time series (one JSON object per row, partitioned by effective date and de-duplicated; FX, metals, crypto, rates and yields stacked into one queryable table, with annual NDJSON.gz + Parquet roll-ups) — is maintained privately and offered separately. It is not served on this public CDN. The format is documented by schema/observations.schema.json for consumers who receive it.

License

Code: MIT. Data is published by each institution under its own terms — the UN, BIS, ECB, LBMA, Swissquote, CoinGecko, the New York Fed and the U.S. Treasury as attributed above. Use the data subject to those institutions' respective licenses.