Rn Debug Mcp

Let AI agents see, understand, and interact with your React Native app running on Android emulator or iOS simulator — through a single MCP server.

Point your MCP client at this server and an agent can connect to your app, read logs, inspect the UI, tap buttons, type text, scroll, take screenshots, and reload — all without leaving the conversation.

https://github.com/user-attachments/assets/0d5a5235-9c67-4d79-b30f-de0132be06cd

Features

Connect and Control

• Android + iOS — one server handles both platforms
• Multi-session — debug multiple devices or apps at the same time
• Hot reload — reload your app instantly via Metro; automatic fallback to native reload when Metro is unavailable

See What's Happening

• Live logs — stream device logs in real time (Android logcat / iOS simctl)
• Error filtering — surface only errors so the agent focuses on what matters
• Network inspector — capture HTTP requests and responses with cursor-based polling
• Screenshots — capture the screen as a PNG image the agent can see inline

Understand the UI

• UI tree — get the full view hierarchy (Android UIAutomator / iOS WebDriverAgent)
• Visible elements — list what's on screen with text, bounds, and testIDs
• Screen context — get the current activity/screen name so the agent knows where it is

Interact with the App

• Tap, scroll, type, back — drive the app like a real user
• Tap by testID — target elements by testID instead of fragile coordinates
• testID discovery — list all testIDs on screen, search by exact or partial match
• testID remediation — when a testID is missing, the agent gets a ready-to-paste code fix and can reload to verify

Requirements

• Node.js 20+
• Android SDK / adb on PATH
• Xcode command line tools (xcrun) and iOS Simulator (for iOS)
• React Native app running on emulator/simulator
• Metro running (default: 8081)
• WebDriverAgent reachable for iOS (default: http://127.0.0.1:8100)

Quickstart

Option A: Global install (use from any project)

npm install -g rn-debug-mcp

Add to your MCP client config:

{
  "mcpServers": {
    "rn-debug": {
      "command": "npx",
      "args": ["-y", "rn-debug-mcp"],
      "env": {
        "WDA_BASE_URL": "http://127.0.0.1:8100"
      }
    }
  }
}

Option B: Local dev dependency (per-project)

npm install -D rn-debug-mcp
npm run build

Add to your MCP client config:

{
  "mcpServers": {
    "rn-debug": {
      "command": "node",
      "args": ["/ABS/PATH/TO/node_modules/rn-debug-mcp/dist/src/index.js"],
      "env": {
        "WDA_BASE_URL": "http://127.0.0.1:8100"
      }
    }
  }
}

iOS Support

iOS works automatically on first connect_app({ platform: "ios" }). WebDriverAgent sources are cloned and built transparently if not already present.

• If WDA is already running on :8100 (or the configured WDA_BASE_URL), the install/build is skipped entirely.
• Set WDA_NO_AUTO_INSTALL=1 to disable automatic installation and require manual setup.
• Set WDA_BASE_URL to point to an externally managed WebDriverAgent instance.

Manual / Advanced Setup

Install WDA sources manually:

npx --no-install rndmcp install wda

Run WDA standalone:

npm run ios:wda

Optional overrides:

WDA_PROJECT_PATH="/abs/path/to/WebDriverAgent.xcodeproj" npm run ios:wda
WDA_DEVICE_ID="<booted-simulator-udid>" npm run ios:wda
WDA_DESTINATION='platform=iOS Simulator,name=iPhone 16' npm run ios:wda

Tools

Session and Connection

• connect_app({ platform?, deviceId?, metroPort? })
• list_sessions({})
• set_active_session({ sessionId })
• close_session({ sessionId })
• get_connection_status({ sessionId? })
• disconnect_app({ sessionId? })
• reload_app({ sessionId? })

Logs, Errors, and Network

• get_logs({ sessionId?, sinceCursor?, limit?, levels?, tags?, sources? })
• get_errors({ sessionId?, sinceCursor?, limit?, levels?, tags?, sources? })
• get_network_requests({ sessionId?, sinceCursor?, limit?, phases?, methods?, statuses?, urlContains?, sources? })

UI and Context

• get_screen_context({ sessionId? })
• get_ui_tree({ sessionId?, maxDepth?, maxNodes? })
• get_visible_elements({ sessionId?, maxDepth?, maxNodes?, limit?, clickableOnly?, includeTextless?, skipVisibilityCheck?, testId?, testIdMatch? })
• get_screen_test_ids({ sessionId?, maxDepth?, maxNodes?, limit?, includeNonClickable?, includeInvisible? })
• get_elements_by_test_id({ sessionId?, testId, maxDepth?, maxNodes?, limit?, clickableOnly?, includeTextless?, skipVisibilityCheck?, testIdMatch? })
• get_test_id_remediation_plan({ sessionId?, desiredAction, desiredTestId?, matchMode? })

Interaction

• tap({ sessionId?, x, y })
• tap_element({ sessionId?, elementId, maxDepth?, maxNodes? })
• type_text({ sessionId?, text, submit? })
• press_back({ sessionId? })
• scroll({ sessionId?, direction, distanceRatio?, durationMs? })
• take_screenshot({ sessionId? })

Recommended Agent Flow (testID-first)

1. get_elements_by_test_id with testIdMatch: "exact".
2. If unknown IDs, call get_screen_test_ids.
3. If empty, retry get_elements_by_test_id with testIdMatch: "contains".
4. If still empty:
   • call get_screen_context
   • call get_test_id_remediation_plan
   • patch app code with suggested testID
   • call reload_app
   • retry exact testID lookup
5. If unresolved:
   • try tap_element from visible candidates
   • fallback to tap({ x, y })
   • use scroll, press_back, and type_text for navigation/input

testID naming convention: screen.element.action (example: checkout.submit.button).

Platform Notes

• connect_app defaults to platform: "android" for backward compatibility.
• iOS tap coordinates use point space (WDA coordinates), not screenshot pixels.
• If converting screenshot pixels to iOS points:
  • pointX = round(pixelX / scaleFactor)
  • pointY = round(pixelY / scaleFactor)
• get_elements_by_test_id defaults:
  • skipVisibilityCheck: true (RN-friendly)
  • clickableOnly: false (broader matching)
• get_screen_test_ids default: includeInvisible: true.

Development

npm run typecheck
npm test

CLI usage:

rndmcp                   # Start MCP server over stdio
rndmcp install wda       # Clone WebDriverAgent into this package

Troubleshooting

• iOS connect reports missing WDA:
  • WDA is auto-installed on first connect_app({ platform: "ios" }) unless WDA_NO_AUTO_INSTALL=1
  • set WDA_BASE_URL to an already running WDA, or
  • run rndmcp install wda and then npm run ios:wda for manual setup
• Reload fallbacks:
  • Android: ADB broadcast/key events
  • iOS simulator: Cmd+R keyboard trigger via osascript