React DevTools

Inspect running React apps. See actual props, state, hooks - not just source code.

When to Use

Use these tools when:

• User says "why doesn't this update" or "state is wrong"
• Behavior doesn't match what code suggests
• Need to verify actual runtime values
• Debugging performance / excessive renders
• Exploring unfamiliar React codebase

Don't use when:

• Bug is obvious from source (missing dep, typo)
• Just need to read/edit files
• No React app is running

Setup Check

Before using, ensure:

1. MCP server is configured in .mcp.json
2. React app is running with DevTools connected

Core Workflow

1. Connect

connect()

2. Find the component

search_components({ query: "ComponentName" })

or

get_component_tree()

3. Inspect it

inspect_element({ id: <element_id> })

Returns: { props, state, hooks, context }

Common Debugging Patterns

"Why doesn't clicking X update Y?"

1. search_components({ query: "ButtonComponent" })
2. inspect_element({ id }) → check state/props
3. Compare actual values vs expected

"This component re-renders too much"

1. start_profiling()
2. [user interacts with app]
3. stop_profiling() → see render counts and timing

"What's the actual value of this state?"

1. search_components({ query: "ComponentName" })
2. inspect_element({ id })
3. Look at hooks[].value for useState values

"Who renders this component?"

get_owners_list({ id }) → shows parent chain

Key Tools

Tips

• Element IDs change on hot reload - re-search after code changes
• Use highlight_element to confirm you're looking at the right component
• Hooks are indexed - hooks[0] is first useState/useEffect in component