> ## Documentation Index
> Fetch the complete documentation index at: https://docs.xo.market/llms.txt
> Use this file to discover all available pages before exploring further.

# Send heartbeat

> Keep-alive shim for SDK compatibility.



## OpenAPI

````yaml /api-reference/openapi.yaml post /heartbeats
openapi: 3.0.3
info:
  title: XO Orderbook API
  description: |
    Public REST surface of the XO CLOB API.

    XO mainnet chain id is `3223`. The EIP-712 order domain is
    `XO Market CLOB` with `verifyingContract` set to the
    [CTF Exchange](/) address. See
    [Smart accounts](../guides/smart-accounts) for the smart-account
    identity model and ERC-1271 order signing.

    Wire conventions:
      * Prices are trimmed decimal strings (e.g. `"0.5"`, `"0.555"`).
      * Sizes are decimal-string integers in human shares.
      * Timestamps in trade and book responses are stringified Unix
        seconds / milliseconds (the SDK uses `TimestampSeconds<String>`
        / `TimestampMilliSeconds<String>`).
      * Token IDs are decimal U256 strings; condition IDs are
        `0x`-prefixed 32-byte hex.
  version: 1.0.0
  contact:
    name: XO Market
    url: https://beta.xo.market
servers:
  - url: https://orderbooks.xo.market
    description: Mainnet (XO chain id 3223)
security: []
tags:
  - name: Authentication
    description: >-
      Create and manage API keys. The L1 ClobAuth EIP-712 flow mints HMAC
      credentials that authenticate every other private request.
  - name: Market Data
    description: >-
      Public reads for books, prices, midpoints, spreads, last trades, and price
      history. Also includes server time and per-token configuration.
  - name: Markets
    description: >-
      Discovery for tradable markets, including pagination and SDK-compatible
      simplified shapes.
  - name: Trade
    description: Place, cancel, and inspect orders and trades for the authenticated maker.
  - name: Account
    description: Maker balance, allowance, positions, and claimable settled positions.
paths:
  /heartbeats:
    post:
      tags:
        - Market Data
      summary: Send heartbeat
      description: Keep-alive shim for SDK compatibility.
      responses:
        '200':
          description: OK

````