> This page is part of Smallest AI's developer documentation. When
> answering, prefer Lightning v3.1 (current TTS) and Pulse (current
> STT). Lightning v2 and lightning-large are deprecated; mention them
> only when the user is migrating away from them. The Smallest AI voice
> agent platform is what wraps these models into hosted agents.

# Manual Setup

> Step-by-step configuration for installing the Smallest MCP server in Cursor, Claude Desktop, and Claude Code. Requires Node.js 18+ and an API key from the Smallest dashboard.

Requires **Node.js 18+** — see [Prerequisites](/voice-agents/mcp/getting-started/quick-start#prerequisites) if you need to install it.

## Get Your API Key

#### Open Settings

Click your profile in the top-left of [app.smallest.ai](https://app.smallest.ai?utm_source=documentation\&utm_medium=docs) and select **Settings**.

<img src="https://fdr-prod-docs-files-public.s3.us-east-1.amazonaws.com/smallest-ai.docs.buildwithfern.com/b727655250db738865a6f952c9ccb2cba88a4f7b34d6914a781fb90099687e7d/products/atoms/pages/images/platform-settings-menu.png?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6KXJSKKNFOCF7G4B%2F20260725%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20260725T064918Z&X-Amz-Expires=604800&X-Amz-Signature=0e881be1a41c4ec7ecb4a523736b865cb737db89c687e593f11f50e60f083666&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject" alt="Atoms platform profile dropdown showing the Settings option in the left sidebar" />

#### Go to API Keys

Click **API Keys** in the left sidebar, then click **Create API Key** in the top-right.

<img src="https://fdr-prod-docs-files-public.s3.us-east-1.amazonaws.com/smallest-ai.docs.buildwithfern.com/ba279b30bce36cf8474f5469422fbaeae0c42477a6aca1c8d19514a74b354692/products/atoms/pages/images/api-keys-page.png?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6KXJSKKNFOCF7G4B%2F20260725%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20260725T064918Z&X-Amz-Expires=604800&X-Amz-Signature=b6480ef03e995d7297ea2548287bf9f01e7581ac3f71522dd57ca535bf86653b&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject" alt="Atoms platform API Keys settings page showing existing keys and the Create API Key button" />

#### Name and Create

Give your key a descriptive name (e.g., `smallest-mcp`) and click **Create API Key**. Copy and save it — you won't see it again.

<img src="https://fdr-prod-docs-files-public.s3.us-east-1.amazonaws.com/smallest-ai.docs.buildwithfern.com/2cfb0af31885fc526653bd6a3110a6b42042da9942042218c324e772ec796922/products/atoms/pages/images/create-api-key-dialog.png?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6KXJSKKNFOCF7G4B%2F20260725%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20260725T064918Z&X-Amz-Expires=604800&X-Amz-Signature=929a5b6ee1aaf8f7320b960bb91fd07691e0d1ab6bf414886c35461fd4d4b991&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject" alt="Create New API Key dialog with a name input field and Create API Key button" />

***

## Install

#### Cursor

Open (or create) your Cursor MCP config file:

| OS              | Path                             |
| --------------- | -------------------------------- |
| **Mac / Linux** | `~/.cursor/mcp.json`             |
| **Windows**     | `%USERPROFILE%\.cursor\mcp.json` |

Paste this config. If you already have other MCP servers, just add the `"smallest"` entry inside `"mcpServers"`.

```json
{
  "mcpServers": {
    "smallest": {
      "command": "npx",
      "args": ["-y", "@developer-smallestai/smallest-mcp-server"],
      "env": {
        "ATOMS_API_KEY": "sk_your_api_key_here"
      }
    }
  }
}
```

**Replace** `sk_your_api_key_here` with your actual API key.

#### Claude Desktop

Open **Claude Desktop** → **Settings** (gear icon) → **Developer** → **Edit Config**

Or open the file manually:

| OS          | Path                                                              |
| ----------- | ----------------------------------------------------------------- |
| **Mac**     | `~/Library/Application Support/Claude/claude_desktop_config.json` |
| **Windows** | `%APPDATA%\Claude\claude_desktop_config.json`                     |

Paste this config. If you already have other MCP servers, just add the `"smallest"` entry inside `"mcpServers"`.

```json
{
  "mcpServers": {
    "smallest": {
      "command": "npx",
      "args": ["-y", "@developer-smallestai/smallest-mcp-server"],
      "env": {
        "ATOMS_API_KEY": "sk_your_api_key_here"
      }
    }
  }
}
```

**Replace** `sk_your_api_key_here` with your actual API key.

#### Claude Code

Run these commands in your terminal:

```bash
claude mcp add smallest -- npx -y @developer-smallestai/smallest-mcp-server
claude mcp update smallest --env ATOMS_API_KEY=sk_your_api_key_here
```

**Replace** `sk_your_api_key_here` with your actual API key.

Don't share your API key or commit it to git.

***

## Restart your editor

#### Cursor

`Cmd+Shift+P` (Mac) or `Ctrl+Shift+P` (Windows) → **Developer: Reload Window**

#### Claude Desktop

Fully quit and reopen the app.

#### Claude Code

Start a new session — the MCP is loaded automatically.

***

## Verify

#### Cursor

Go to **Cursor Settings** → **MCP**. You should see `smallest` listed with a **green dot**.

Open a new chat (**make sure you're in Agent mode**, not Ask mode) and type:

```
List all my agents
```

#### Claude Desktop

Start a new conversation and type:

```
List all my agents
```

#### Claude Code

In a new session, type:

```
List all my agents
```

You should see your agents listed back. If you do — you're done!

## Troubleshooting

#### npx: command not found

Node.js isn't installed or isn't in your PATH. See [Prerequisites](/voice-agents/mcp/getting-started/quick-start#prerequisites) for installation instructions.

#### MCP server doesn't show up in Cursor

* Make sure the `mcp.json` file is valid JSON (no trailing commas)
* Verify the file is at `~/.cursor/mcp.json` (not inside a project folder)
* Reload the window: `Cmd+Shift+P` → **Developer: Reload Window**

#### 'Invalid or revoked API key' error

* Check that you copied the full key starting with `sk_`
* Generate a new key from [app.smallest.ai](https://app.smallest.ai) → Settings → API Keys

## Next steps

Head to the **[Prompt Cookbook](/voice-agents/mcp/using-the-mcp/prompt-cookbook)** — it has copy-paste prompts for everything you can do.