Harness FME MCP Server

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A Harness FME (Split.io) MCP server — read and toggle feature flags from your AI assistant

Features • Quick Start • Installation • Tools • Development

🌟 Features

• 🚩 Feature Flag Management - List, inspect, kill, and restore flags across any workspace
• 🔐 Simple Authentication - Single API key, zero config friction
• 🌍 Multi-Workspace Support - Work across any number of Harness FME workspaces
• 🌿 Environment-Aware - Target flags in specific environments (staging, production, etc.)
• ⚡ Modern Stack - TypeScript 5+, ES2023, Native Fetch API, ESM
• 📦 MCP Protocol - Native integration with Claude Desktop, Claude Code CLI, Cursor, and more
• 🔒 Safety Guard - Kill operations require explicit confirm: true — no accidental flag kills

🚀 Quick Start

Prerequisites

• Node.js 20+
• A Harness FME API key (how to get one)

Installation

Option 1: Via npm (recommended):

# No installation needed — just use npx in your MCP config
npx --yes @kud/mcp-harness-fme@latest

Option 2: Local installation:

git clone https://github.com/kud/mcp-harness-fme.git
cd mcp-harness-fme
npm install
npm run build

Quick Setup Example (Claude CLI)

claude mcp add --transport stdio --scope user harness-fme \
  --env HARNESS_FME_API_KEY=your_api_key \
  -- npx --yes @kud/mcp-harness-fme@latest

✅ Done! Now you can inspect and toggle feature flags from any AI assistant.

📚 Installation Guides

Choose your development environment:

• Claude Code CLI - Command line interface
• Claude Desktop - Desktop application
• VSCode - With Cline, Claude Dev, Continue
• Cursor - AI-first IDE
• Windsurf - AI-powered code editor
• JetBrains IDEs - IntelliJ, WebStorm, PyCharm, GoLand, etc.

🎯 Claude Code CLI

For: Claude AI via command line interface

claude mcp add --transport stdio --scope user harness-fme \
  --env HARNESS_FME_API_KEY=your_api_key \
  -- npx --yes @kud/mcp-harness-fme@latest

If installed locally:

claude mcp add --transport stdio --scope user harness-fme \
  --env HARNESS_FME_API_KEY=your_api_key \
  -- node ~/path/to/mcp-harness-fme/dist/index.js

Verify: claude mcp list should show harness-fme

🖥️ Claude Desktop

For: Claude AI desktop application

1. Open Configuration File

macOS:

open ~/Library/Application\ Support/Claude/claude_desktop_config.json

Windows:

notepad %APPDATA%\Claude\claude_desktop_config.json

2. Add Configuration

Via npm (recommended):

{
  "mcpServers": {
    "harness-fme": {
      "command": "npx",
      "args": ["--yes", "@kud/mcp-harness-fme@latest"],
      "env": {
        "HARNESS_FME_API_KEY": "your_api_key"
      }
    }
  }
}

Local installation:

{
  "mcpServers": {
    "harness-fme": {
      "command": "node",
      "args": ["/absolute/path/to/mcp-harness-fme/dist/index.js"],
      "env": {
        "HARNESS_FME_API_KEY": "your_api_key"
      }
    }
  }
}

3. Restart

Quit (Cmd+Q / Alt+F4) and reopen Claude Desktop.

📝 VSCode

For: VSCode with MCP-compatible extensions (Cline, Claude Dev, Continue)

Settings (Cmd+, / Ctrl+,) → Search "Cline: MCP Settings" → Edit in settings.json:

{
  "cline.mcpServers": {
    "harness-fme": {
      "command": "npx",
      "args": ["--yes", "@kud/mcp-harness-fme@latest"],
      "env": {
        "HARNESS_FME_API_KEY": "your_api_key"
      }
    }
  }
}

Reload window after configuration.

🌐 Cursor

For: Cursor IDE with built-in AI

Settings (Cmd+, / Ctrl+,) → Search "MCP" → Edit Config or open ~/.cursor/mcp_config.json:

{
  "mcpServers": {
    "harness-fme": {
      "command": "npx",
      "args": ["--yes", "@kud/mcp-harness-fme@latest"],
      "env": {
        "HARNESS_FME_API_KEY": "your_api_key"
      }
    }
  }
}

Restart Cursor after configuration.

🌊 Windsurf

For: Windsurf AI-powered code editor

Settings → AI Settings → Model Context Protocol → Add Server:

{
  "mcpServers": {
    "harness-fme": {
      "command": "npx",
      "args": ["--yes", "@kud/mcp-harness-fme@latest"],
      "env": {
        "HARNESS_FME_API_KEY": "your_api_key"
      }
    }
  }
}

Or edit ~/.windsurf/mcp_settings.json directly. Restart Windsurf after configuration.

🔧 All JetBrains IDEs

For: IntelliJ IDEA, WebStorm, PyCharm, GoLand, RubyMine, PhpStorm, Rider, CLion, DataGrip

Settings (Cmd+, / Ctrl+,) → Tools → AI Assistant → Model Context Protocol → Add Server:

• Name: harness-fme
• Command: npx
• Arguments: --yes @kud/mcp-harness-fme@latest
• Environment Variables:

  HARNESS_FME_API_KEY=your_api_key

For local installation, use Command: node and Arguments: /absolute/path/to/mcp-harness-fme/dist/index.js

Apply and restart the IDE.

🛠️ Available Tools

🏢 Workspaces (1 tool)

| Tool | Description | | ----------------- | -------------------------------------- | | list_workspaces | List all FME workspaces in the account |

🌍 Environments (1 tool)

| Tool | Description | | ------------------- | ------------------------------------ | | list_environments | List all environments in a workspace |

🚩 Feature Flags (9 tools)

| Tool | Description | | ------------------------ | ----------------------------------------------------------------------- | | list_feature_flags | List feature flags in a workspace (supports tag filter, pagination) | | get_feature_flag | Get metadata for a specific feature flag | | create_feature_flag | Create a new feature flag for a given traffic type | | update_feature_flag | Update a flag's description, tags, or owners | | delete_feature_flag | Permanently delete a feature flag (requires confirm: true) | | list_flag_definitions | List all flag definitions (targeting rules) in an environment | | get_flag_definition | Get targeting rules and treatment definition in an environment | | create_flag_definition | Activate a flag in an environment with treatments and targeting rules | | update_flag_definition | Fully replace a flag's targeting rules in an environment | | delete_flag_definition | Remove a flag definition from an environment (requires confirm: true) | | kill_feature_flag | Kill (disable) a flag — forces all traffic to default treatment | | restore_feature_flag | Restore (re-enable) a killed feature flag |

🧩 Segments (1 tool)

| Tool | Description | | --------------- | -------------------------------- | | list_segments | List all segments in a workspace |

🔀 Traffic Types (1 tool)

| Tool | Description | | -------------------- | ------------------------------------- | | list_traffic_types | List all traffic types in a workspace |

Total: 16 Tools covering full feature flag lifecycle management.

💬 Example Conversations

Once configured, interact with your feature flags naturally:

You: "List all my workspaces"
AI:  Shows all FME workspaces with IDs

You: "List all feature flags in workspace ws_abc123"
AI:  Shows all flags with pagination

You: "Search for flags containing 'dark-mode'"
AI:  Returns matching flags

You: "What are the targeting rules for 'checkout-redesign' in production?"
AI:  Shows treatments, targeting rules, percentage splits

You: "Kill the 'new-payments-flow' flag in production"
AI:  Requires confirm=true, then disables the flag

You: "Restore 'new-payments-flow' in production"
AI:  Re-enables the flag and resumes normal traffic routing

🧪 Development

Project Structure

mcp-harness-fme/
├── src/
│   └── index.ts          # MCP server — all tools in one file
├── dist/                 # Compiled output
├── package.json
├── tsconfig.json
└── README.md

Available Scripts

| Script | Description | | --------------------- | -------------------------------- | | npm run build | Compile TypeScript to JavaScript | | npm run build:watch | Watch mode — rebuild on changes | | npm run dev | Run in development (tsx) | | npm start | Run compiled server | | npm run inspect | Open MCP inspector | | npm run inspect:dev | Inspector in dev mode (no build) | | npm run typecheck | Type check without building | | npm run clean | Remove build artifacts |

Development Workflow

# Terminal 1: Watch mode
npm run build:watch

# Terminal 2: Test with inspector
export HARNESS_FME_API_KEY=your_api_key
npm run inspect:dev

Opens http://localhost:5173 — test all tools interactively!

Adding New Tools

1. Open src/index.ts
2. Call server.registerTool(...) with your tool name, schema, and handler
3. Rebuild: npm run build

⚙️ Configuration

Environment Variables

| Variable | Required | Description | | --------------------- | -------- | ------------------------ | | HARNESS_FME_API_KEY | ✅ Yes | Your Harness FME API key |

The server exits immediately at startup if the key is missing — no silent failures.

🔐 Authentication

Getting Your Harness FME API Key

1. Log in to your Harness FME account
2. Go to Admin Settings → API Keys
3. Click Add API Key
4. Select type Admin (required for management operations)
5. Copy the key — store it somewhere safe

⚠️ Important: Admin API keys have full read/write access to your workspace. Treat them like passwords. Never commit them to version control.

Setting the Key

In your shell:

export HARNESS_FME_API_KEY=your_api_key

In MCP config (recommended):

"env": {
  "HARNESS_FME_API_KEY": "your_api_key"
}

🐛 Troubleshooting

Server Not Showing in Claude

1. ✅ Check HARNESS_FME_API_KEY is set
2. ✅ Run npm install && npm run build
3. ✅ Restart Claude completely

Authentication Errors

# Test your key directly
curl -H "Authorization: Bearer your_api_key" \
  https://api.split.io/internal/api/v2/workspaces

If this returns JSON, your key is valid.

Build Errors

npm run clean && npm run build

Check Logs

Claude Desktop logs:

• macOS: ~/Library/Logs/Claude/mcp*.log
• Windows: %APPDATA%\Claude\logs\mcp*.log

Claude Code CLI:

claude mcp get harness-fme

🔒 Security Best Practices

• ✅ Use environment variables — never hardcode API keys
• ✅ Never commit your API key to version control
• ✅ Rotate keys regularly via the Harness admin panel
• ✅ Use the confirm: true guard on kill operations — it's there for a reason
• ✅ Protect your MCP config files (claude_desktop_config.json, etc.)

📊 Tech Stack

• Runtime: Node.js 20+
• Language: TypeScript 5+
• Target: ES2023
• Protocol: MCP 1.10 (stdio transport)
• HTTP Client: Native Fetch API
• Module System: ESM
• Schema Validation: Zod

🤝 Contributing

Contributions welcome! Please ensure:

1. TypeScript strict mode compliance
2. All tools properly typed with Zod schemas
3. Build passes: npm run build
4. No breaking changes to existing tool signatures

📄 License

MIT License — see LICENSE file

🙏 Acknowledgments

• Built with Model Context Protocol
• Powered by the Harness FME (Split.io) REST API

📮 Support

• 🐛 Issues: GitHub Issues
• 💬 Discussions: GitHub Discussions

Made with ❤️ for the feature flag community

⭐ Star this repo if it helped you!

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