# Connect a Client

> Point an MCP client at your endpoint.

Assume the [quick start](/guide) server is listening on `http://localhost:3000/mcp`.

## MCP Inspector

The fastest way to see what your server exposes:

```sh
npx @modelcontextprotocol/inspector
```

Choose the **Streamable HTTP** transport and enter `http://localhost:3000/mcp`. If [auth](/security/auth) is enabled, add the header there — `Authorization: Bearer <token>` or `x-api-key: <token>`.

## Claude Code

```sh
claude mcp add --transport http my-server http://localhost:3000/mcp
```

With auth:

```sh
claude mcp add --transport http my-server http://localhost:3000/mcp \
  --header "Authorization: Bearer $MCP_TOKEN"
```

## A stdio-Only Client

Clients that only speak stdio need a bridge. [`mcp-remote`](https://www.npmjs.com/package/mcp-remote) is the usual one:

```json [claude_desktop_config.json]
{
  "mcpServers": {
    "my-server": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "http://localhost:3000/mcp"]
    }
  }
}
```

## Origin Headers

A browser-based client sends `Origin`, and [origin validation](/security/origin) will reject it unless allowlisted. This is the single most common "it works with curl but not in the app" cause:

```ts
defineMcpHandler({
  name: "my-server",
  version: "1.0.0",
  origin: { allow: ["http://localhost:6274"] }, // e.g. the Inspector's own origin
  tools: [/* ... */],
});
```

## Checking It Yourself

No client needed — one `POST` tells you whether the endpoint is healthy:

```sh
curl -X POST http://localhost:3000/mcp \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -H 'mcp-protocol-version: 2026-07-28' \
  -H 'mcp-method: server/discover' \
  -d '{ "jsonrpc": "2.0", "id": 1, "method": "server/discover",
        "params": { "_meta": {
          "io.modelcontextprotocol/protocolVersion": "2026-07-28",
          "io.modelcontextprotocol/clientCapabilities": {} } } }'
```

:read-more{to="/examples/curl-requests" title="More raw requests"}

## Testing Without a Network

H3 apps can be called directly, which makes an MCP endpoint trivial to unit-test:

```ts
const res = await app.request("/mcp", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({ jsonrpc: "2.0", id: 1, method: "tools/list" }),
});

console.log(await res.json());
```