Claude Code / AI Coding Tools
Claude Code MCP Tool Not Registered — "No handler registered for 'mcp__tools'"
Fix Claude Code failing to execute because an MCP server tool is not recognized or registered by the CLI Includes evidence for Claude Code troubleshooting demand.
- Category
- AI Coding Tools
- Error signature
No handler registered for 'mcp__tools' / MCP tool not registered- Quick fix
- Compare the failing environment with a known working setup, then change one configuration value at a time.
- Updated
What this error means
No handler registered for 'mcp__tools' / MCP tool not registered is a Claude Code failure pattern reported for developers trying to fix claude code failing to execute because an mcp server tool is not recognized or registered by the cli. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.
Why this happens
Real Claude Code workflow error where users configure MCP servers but tools fail to register, blocking AI-assisted file operations. Distinct from Covered: ‘Cursor model not available’ and ‘Claude Code auth’. Category mapped to AI Coding Tools per rules.
Common causes
- Real Claude Code workflow error where users configure MCP servers but tools fail to register, blocking AI-assisted file operations. Distinct from Covered: ‘Cursor model not available’ and ‘Claude Code auth’. Category mapped to AI Coding Tools per rules.
Quick fixes
- Confirm the exact error signature matches
No handler registered for 'mcp__tools' / MCP tool not registered. - Check the Claude Code account, local tool state, and provider configuration involved in the failing workflow.
- Compare the failing environment with a known working setup, then change one configuration value at a time.
Platform/tool-specific checks
- Verify the command, editor, extension, or API client that produced the error.
- Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
- Avoid deleting credentials, local model data, or project settings until the failing scope is clear.
Step-by-step troubleshooting
- Capture the exact error message and the command, editor action, or request that triggered it.
- Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
- Review the source evidence below and compare it with your environment.
- Apply one change at a time and rerun the smallest failing action.
- Keep the working fix documented for the team or deployment environment.
How to prevent it
- Keep provider/tool configuration documented.
- Record non-secret diagnostics such as tool version, provider name, model name, and command path.
- Add a lightweight check before CI or production workflows depend on the tool.
Sources checked
Evidence note: Real Claude Code workflow error where users configure MCP servers but tools fail to register, blocking AI-assisted file operations. Distinct from Covered: ‘Cursor model not available’ and ‘Claude Code auth’. Category mapped to AI Coding Tools per rules.
Related errors
- AI Coding Tools
FAQ
What should I check first?
Start with the exact No handler registered for 'mcp__tools' / MCP tool not registered text and the smallest action that reproduces it.
Can I ignore this error?
No. Treat it as a failed Claude Code workflow until the root cause is understood.
Is this guaranteed to have one fix?
No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.
How do I know the fix worked?
Rerun the same command, editor action, or request. The fix is working when that action completes without No handler registered for 'mcp__tools' / MCP tool not registered.