Developers

Build on MonoChat with APIs, functions and your own AI agents.

Connect your systems with the REST API and webhooks, write custom functions in JavaScript, give AI agents your tools through function tools and MCP, and run the agent framework you prefer on WhatsApp and every other channel.

Read the SDK docs Start free
  • REST API
  • Webhooks
  • JavaScript SDK
  • MCP
  • Agent Harness

The building blocks

Everything a developer can extend, from a single API call to an agent that works a case end to end.

Custom functions

Write your own logic in JavaScript

Every function receives an sdk object. What it offers depends on where the function runs: in the browser or on the server.

  • Client SDK for browser functions, mainly Custom Views
  • Server SDK for every other function type
  • Function types: Custom Flow Node, Server Side Method, Custom View, AI Tool, Cron Job and Custom App Setup
  • Server Side Methods can be exposed as API endpoints for your other systems
SDK overview Custom functions
Example request
POST https://app.monochat.ai/api/<slug>/custom-functions/template-app/api/template/send.js
Authorization: Bearer <API_TOKEN>
Content-Type: application/json

Sending an approved WhatsApp template with the WhatsApp Template API app. Your tenant slug is the part after /tenants/ in your MonoChat address.

Bring your own agent

Your agent framework, on every channel

Add an AI Harness once, then use it from an AI Agent node in any flow or start runs from code. MonoChat brings the conversations, the channels and the handover to your team.

  • Seven harness providers: MonoChat, OpenAI Agents SDK, Claude Agent SDK, Pi, OpenAI Agents API, Claude Managed Agents and Custom
  • Custom: your own server built with LangGraph, Google ADK, CrewAI or your own code, connected with an endpoint URL and a shared secret
  • Main, fallback and fast models per agent node, and a budget for every run
  • Start, read and cancel runs from custom functions and API clients; every run is recorded with its model calls, tool calls and result
Explore the Agent Harness AI agents in the docs

Developer APIs

Two API-only apps for your own systems

Install them from MonoStore and call them with an API token from Profile › API Tokens.

Quick start

From a free workspace to your first API call or agent.

  1. Open a workspace

    Sign up at app.monochat.ai and start on the free plan.

  2. Connect a channel

    Connect WhatsApp, Instagram, web chat or any other channel you want to build for.

  3. Create an API token

    Create a token under Profile › API Tokens. It is shown only once, so copy it right away.

  4. Build

    Install a developer app, write a function, or add an MCP client or AI Harness under Settings › Automation.

Documentation

Reference and guides on support.monochat.ai.

FAQ

Developer questions

What you can build, and how.

Does MonoChat have an API?

Yes. MonoChat offers REST endpoints and webhook events for integrations, custom functions whose server-side methods can be exposed as API endpoints, and API-only apps such as WhatsApp Template API and Session Link. API calls use a token you create under Profile › API Tokens.

Which language are custom functions written in?

JavaScript. Each function receives an sdk object: the Client SDK for browser functions such as Custom Views, and the Server SDK for flow nodes, server-side methods, AI tools, cron jobs and custom app setup.

How do I send a WhatsApp template message from my own system?

Install the WhatsApp Template API app, create an API token, call template/list.js to see your approved templates and template/send.js to send one. When the customer replies, the conversation lands in your MonoChat inbox.

Can I connect my own MCP server?

Yes. Add it under Settings › Automation › AI MCP Clients with its endpoint and, if needed, Basic or Bearer authentication. MonoChat connects over the SSE transport, reads the server’s tools and lets you give them to AI nodes and AI Agent nodes.

Can I run an agent built with the Claude Agent SDK, OpenAI Agents SDK or LangGraph?

Yes. Choose the Claude Agent SDK or OpenAI Agents SDK as the harness provider, or choose Custom and enter your endpoint URL and a shared secret for an agent built with LangGraph, Google ADK, CrewAI or your own code.

Can I start an AI agent from code?

Yes. Custom functions and API clients can start, read and cancel agent runs with the aiAgentRuns create, show and cancel methods. Every run is recorded in Settings › Automation › AI Agent Runs.

Can MonoChat engineers build the integration for us?

Yes. Development Packs are prepaid MonoChat development days for integrations, automations and custom features. They never expire and can be combined.

Keep exploring

First month of Growth on us

Start building on MonoChat

Open a free workspace, create an API token and make your first call today.

Start with $150 credit Talk to our team

One code per business • 30 days to redeem • No card needed

$150 to get started.

Claim