# Connecting

> Connection lifecycle, state, events, and reconnection for the MCP client.

The MCP client connects to the server over an **SSE transport**: a long-lived
Server-Sent Events stream for server→client messages, plus a message endpoint for
client→server requests. The client handles session setup and reconnection for you.

## Connect and disconnect

```typescript

const mcp = new McpClient({
  serverUrl: "https://mcp.divinci.app",
  autoReconnect: true,
  maxReconnectAttempts: 5,
});

await mcp.connect();
// ... use mcp.tools, mcp.listResources(), etc.
mcp.disconnect();
```

## Connection state

`getState()` returns the current `McpConnectionState`:

```
disconnected → connecting → connected → authenticating → authenticated
```

(or `error`). Helpers:

```typescript
mcp.getState();              // current state
mcp.isConnected();           // transport is up
await mcp.isAuthenticated(); // a valid Auth0 token is present
```

## Events

Register handlers with `on()`:

```typescript
mcp.on({
  onStateChange: (state) => console.log("state:", state),
  onToolsChanged: (tools) => refreshTools(tools),
  onResourcesChanged: (resources) => refreshResources(resources),
  onError: (err) => console.error(err),
});
```

| Event | Fires when |
|-------|-----------|
| `onStateChange(state)` | Connection state changes. |
| `onToolsChanged(tools)` | The server's tool catalog changes. |
| `onResourcesChanged(resources)` | The server's resource list changes. |
| `onError(error)` | A transport or protocol error occurs. |

## Reconnection

With `autoReconnect: true` (the default), dropped SSE connections reconnect with
exponential backoff up to `maxReconnectAttempts`. Tune the base delay and ceiling
through the constructor.

<Aside type="tip">
  Subscribe to `onStateChange` and show a "reconnecting" indicator while the
  client recovers, rather than treating a transient drop as a hard failure.
</Aside>

## Server capabilities

After connecting, inspect what the server supports:

```typescript
const caps = mcp.getServerCapabilities();
console.log(caps?.name, caps?.version, caps?.protocolVersion);
```

## Health check

```typescript
await mcp.ping(); // throws if the connection is unhealthy
```