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Make your first request

A single HTTP call confirms your subscription is active and your API key works.

curl​

curl https://api.onesource.io/api/chain/network-info \
  -H "Authorization: Bearer $ONESOURCE_API_KEY"

Expected response:

{
  "data": {
    "chain_id": "0x1",
    "block_number": "0x14abcde",
    "gas_price": "0x3b9aca00"
  },
  "error": null,
  "meta": { "endpoint": "/api/chain/network-info", "request_id": "..." }
}

block_number is the live mainnet tip; it should be close to the current block reported on https://etherscan.io. To hit the Sepolia testnet instead, add ?network=sepolia to the URL (the chain_id then comes back as 0xaa36a7). See Choosing a network.

Node.js (fetch)​

const res = await fetch('https://api.onesource.io/api/chain/network-info', {
  headers: { Authorization: `Bearer ${process.env.ONESOURCE_API_KEY}` },
});
const { data, error } = await res.json();
if (error) throw new Error(`${error.code}: ${error.message}`);
console.log(`Chain ${parseInt(data.chain_id, 16)} at block ${parseInt(data.block_number, 16)}`);

Python (httpx)​

import os, httpx

resp = httpx.get(
    'https://api.onesource.io/api/chain/network-info',
    headers={'Authorization': f"Bearer {os.environ['ONESOURCE_API_KEY']}"},
)
resp.raise_for_status()
body = resp.json()
print(f"Chain {int(body['data']['chain_id'], 16)} at block {int(body['data']['block_number'], 16)}")

Go​

req, _ := http.NewRequest("GET", "https://api.onesource.io/api/chain/network-info", nil)
req.Header.Set("Authorization", "Bearer "+os.Getenv("ONESOURCE_API_KEY"))

resp, err := http.DefaultClient.Do(req)
if err != nil { return err }
defer resp.Body.Close()

var body struct {
    Data  struct{ ChainID, BlockNumber, GasPrice string } `json:"data"`
    Error *struct{ Code, Message string } `json:"error"`
    Meta  map[string]any `json:"meta"`
}
json.NewDecoder(resp.Body).Decode(&body)

Response envelope​

Every /api/* response uses the same shape:

{ "data": { ... }, "error": null, "meta": { "endpoint": "...", "request_id": "..." } }

On failure, data is null and error is an object with code and message. See Response envelope for the full reference.

What can go wrong​

StatusWhat it meansWhat to do
401Missing or invalid Authorization header.Confirm the env var is set and holds the full key you copied when you created it. If you've lost the key, create a replacement on the dashboard.
403Your plan doesn't cover this endpoint (e.g. still on the Sandbox tier).Subscribe to the Developer plan in app.onesource.io, or call the endpoint with x402 / MPP instead.
5xxUpstream RPC node, facilitator, or unhandled service-side issue.Retry with exponential backoff.

Your per-second rate limit is advisory (watch X-RateLimit-Remaining rather than waiting for a 429), but your monthly quota is enforced: once it's exhausted, calls are rejected until the next cycle. See Rate limits and quotas.

Next​

  • Browse the API Reference for the full endpoint catalog.
  • If you're wiring this into an AI assistant, switch to the MCP server instead of raw REST.