WebSocket API

The WebSocket API speaks JSON-RPC 2.0 with the same methods as MCP, plus subscriptions: the server re-runs a tool on an interval and pushes only when the result changes.

MethodsCopy Anchor Link

initialize, tools/list, tools/call, ping, subscriptions/subscribe, subscriptions/unsubscribe.

Call a toolCopy Anchor Link

{ "jsonrpc": "2.0", "id": 1, "method": "tools/call",
  "params": { "name": "flow_orderbook", "arguments": { "symbol": "BTC" } } }

The result is the tool's JSON object, the same one the REST API returns as its body. There is no text report; that is MCP-only. A tool whose data source fails answers with JSON-RPC error -32004.

SubscribeCopy Anchor Link

{ "jsonrpc": "2.0", "id": 2, "method": "subscriptions/subscribe",
  "params": { "name": "funding_current", "arguments": { "symbol": "BTC" }, "intervalSeconds": 60 } }

The reply returns { "subscriptionId", "intervalSeconds" }. Each time the result changes, the server sends a notifications/subscriptions/update notification carrying { "subscriptionId", "result" } (result is the same JSON object, or error when the data source failed). intervalSeconds defaults to and must be at least 15. Stop with:

{ "jsonrpc": "2.0", "id": 3, "method": "subscriptions/unsubscribe",
  "params": { "subscriptionId": "<id>" } }

Example: Node.jsCopy Anchor Link

import WebSocket from "ws";

const ws = new WebSocket("wss://mcp.f1ow.com/v1/ws", "jsonrpc-2.0", {
  headers: { Authorization: `Bearer ${process.env.F1OW_API_KEY}` },
});

ws.on("open", () => {
  ws.send(JSON.stringify({
    jsonrpc: "2.0", id: 1, method: "subscriptions/subscribe",
    params: { name: "derivatives_open_interest", arguments: { symbol: "ETH" }, intervalSeconds: 60 },
  }));
});

ws.on("message", (raw) => console.log(JSON.parse(raw.toString())));

MeteringCopy Anchor Link

A tools/call costs one unit. A subscription costs one unit per pushed change; checks that find nothing new are free. See pricing & limits.

For agents: this page as Markdown · all docs