econ.yield-curve

Current US Treasury yield curve — the market yield at every constant-maturity tenor from 1 month to 30 years (1M, 3M, 6M, 1Y, 2Y, 3Y, 5Y, 7Y, 10Y, 20Y, 30Y), each as a percent as of its latest date. Also returns the 2s10s spread (10Y − 2Y), the 3m10y spread (10Y − 3M), and an inverted flag (true when 2s10s is negative — a classic recession signal). Daily data. Source: US Treasury constant-maturity rates via FRED (St. Louis Fed).

Overview

The yield curve API is a pay-per-call econ endpoint built for AI agents and autonomous software. Current US Treasury yield curve — the market yield at every constant-maturity tenor from 1 month to 30 years (1M, 3M, 6M, 1Y, 2Y, 3Y, 5Y, 7Y, 10Y, 20Y, 30Y), each as a percent as of its latest date.

There is no signup and no API key. An agent (or any HTTP client) hits the endpoint, receives an x402 "402 Payment Required" challenge, signs a sub-cent USDC payment on Base or Solana, and retries — the data comes back on the paid request. That makes it a drop-in yield curve data source for an agent tool-use loop, an MCP host, or a backend that needs econ data on demand without onboarding to yet another vendor portal.

Use cases

• Give an AI agent live yield curve lookups as a tool, with no API key to provision or rotate — the agent pays per call from a wallet you fund.
• Enrich records in a data pipeline with econ data, paying only for the calls you actually make instead of a monthly seat.
• Ground LLM answers in authoritative econ data to cut hallucination, then optionally request a signed response for verifiability.
• Prototype against the live yield curve API in minutes using the free trial call, then flip to per-call x402 payment for production with no code change.

Code samples

# 1. Probe with no auth → 402 envelope with PaymentRequirements
curl -sS 'https://2s.io/api/econ/yield-curve'

# 2. Sign + retry with PAYMENT-SIGNATURE:
curl -sS 'https://2s.io/api/econ/yield-curve' \
  -H 'PAYMENT-SIGNATURE: <base64-json-payload>'

# Or use the canonical runner (handles probe → sign → retry):
#   EVM_PRIVATE_KEY=0x... node --env-file=.env.local \
#     --experimental-strip-types scripts/x402-pay.ts \
#     'https://2s.io/api/econ/yield-curve'

import { TwoS } from '@2sio/sdk'

const client = new TwoS({
  privateKey: process.env.EVM_PRIVATE_KEY as `0x${string}`,
})

const result = await client.econ.yieldCurve({})

console.log('endpoint:', result.endpoint)
console.log('cost:', result.costUsd, 'USDC')
console.log('tx:', result.settlement?.txHash)
console.log('data:', result.data)

import os
from twosio import TwoS

client = TwoS(private_key=os.environ["EVM_PRIVATE_KEY"])

result = client.econ.yield_curve()

print("endpoint:", result.endpoint)
print("cost:", result.cost_usd, "USDC")
print("tx:", (result.settlement or {}).get("tx_hash"))
print("data:", result.data)

// 1. Add @2sio/mcp to your MCP host config (Claude Desktop example below).
//    EVM_PRIVATE_KEY funds x402 payments per call.

// claude_desktop_config.json
{
  "mcpServers": {
    "2sio": {
      "command": "npx",
      "args": ["-y", "@2sio/mcp"],
      "env": { "EVM_PRIVATE_KEY": "0x..." }
    }
  }
}

// 2. Once the server is running, agents call this tool via standard MCP:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "econ.yield-curve",
    "arguments": {}
  }
}

Response

{
  "ok": true,
  "items": [
    {
      "maturity": "example",
      "months": 1,
      "seriesId": "example",
      "yield": 1,
      "asOf": "example"
    }
  ],
  "total": 1,
  "source": {
    "provider": "example",
    "url": "example",
    "license": "example"
  },
  "meta": {
    "spread2s10s": 1,
    "spread3m10y": 1,
    "inverted": false,
    "asOf": "example"
  }
}

FAQ

Do I need an API key to use the yield curve API?

No. econ.yield-curve is x402-native — there is no signup and no API key. Your client makes the call, receives a 402 with payment requirements, signs a USDC payment, and retries. Funds come from a wallet you control.

How much does the yield curve API cost?

$0.00144 USDC per call, charged per request. There are no monthly fees, seats, or minimums — you pay only for the calls you make.

Can I try the yield curve API for free first?

Yes. Add ?trial=1 (or the header X-2s-Trial: 1) to get a free real call per endpoint per hour, so you can verify the response shape before wiring payment.

Which networks and tokens are supported?

USDC on Base (via EIP-3009 transferWithAuthorization) or Solana (SPL transfer), using the open x402 payment protocol.

How do I call econ.yield-curve from an AI agent or MCP host?

Use @2sio/sdk (TypeScript), 2sio (Python), or the @2sio/mcp server for any MCP host — each handles the probe → sign → retry loop for you. See the code samples on this page.

Discovery

• /api/directory — full catalog of every endpoint
• /openapi.json — OpenAPI 3.1 spec (per-op x-payment-info, x402Payment security)
• /.well-known/x402 — machine-readable service descriptor for x402-aware crawlers
• /.well-known/mcp/server-card.json — MCP SEP-1649 server card
• /llms.txt — plain-text manifest for LLM ingestion