MCP Tools Not Listed: Why tools/list Returns Empty

MCP server connects, but no tools appear? This troubleshooting guide helps you fix issues when tools/list returns empty. Learn how to diagnose auth failures that still allow connection, server selection problems, client caching issues, and when restarts are required.

What "Tools Not Listed" Means

When tools/list returns empty, it means your MCP client successfully connected to the server, but the server isn't providing any tools. This is different from connection failures—the connection works, but tool discovery fails.

Common Causes

• Authentication failures that still allow connection (silent auth errors)
• Wrong server selected or configured
• Client caching old tool list
• Client not restarted after config changes
• Server not fully initialized

Step 1: Check Authentication

Some MCP clients connect even when authentication fails, but then return empty tool lists:

Silent Auth Failures

Connection vs Authentication

Some clients establish a connection even with invalid API keys, but the server returns an empty tool list because authentication failed.

Fix: Verify your API key is correct and active (see 401 Unauthorized guide)

Test Authentication

Verify your API key works with a direct test:

Test with curl

curl -H "Authorization: Bearer YOUR_API_KEY" \
  https://app.corcava.com/mcp

If this returns 401 Unauthorized, your API key is invalid. If it returns tools or 200 OK, authentication is working.

Step 2: Verify Server Selection

Ensure the correct MCP server is selected and configured:

Check Server Configuration

Verify in your MCP config:

• Server name matches what you expect (e.g., "corcava")
• URL is correct: https://app.corcava.com/mcp
• Authorization header is properly formatted
• No typos in server name or configuration

Multiple Server Configuration

If you have multiple MCP servers configured, verify the correct one is active:

Correct Multi-Server Config

{
  "mcpServers": {
    "corcava": {
      "url": "https://app.corcava.com/mcp",
      "headers": {
        "Authorization": "Bearer YOUR_API_KEY"
      }
    },
    "other-server": {
      "url": "https://other-server.com/mcp",
      "headers": {
        "Authorization": "Bearer OTHER_KEY"
      }
    }
  }
}

Ensure "corcava" is listed and configured correctly.

Step 3: Clear Client Cache

MCP clients often cache tool lists. Clear the cache to force a fresh tool discovery:

Client-Specific Cache Clearing

Claude Desktop

1. Quit Claude Desktop completely
2. Clear cache (location varies by OS)
3. Restart Claude Desktop
4. Check if tools appear

Cache locations:

• macOS: ~/Library/Caches/Claude/
• Windows: %APPDATA%\Claude\Cache\
• Linux: ~/.cache/claude/

Cursor

1. Close Cursor completely
2. Clear Cursor cache/storage
3. Restart Cursor
4. Reload window (Cmd/Ctrl+Shift+P → "Reload Window")

Windsurf

1. Close Windsurf completely
2. Clear application cache
3. Restart Windsurf
4. Check MCP server status

Continue

1. Restart Continue extension
2. Clear SSE connection cache
3. Reconnect to MCP server
4. Verify tools appear

Step 4: Restart MCP Client

MCP clients only discover tools on startup. After config changes, a full restart is required:

Restart Requirements

• Full quit required: Not just minimize or close window
• Wait a few seconds: Allow process to fully terminate
• Check system tray: Ensure no background processes remain
• Reopen application: Start fresh to reload config

Verify Restart Worked

After restarting, verify tools are available:

Check tool availability:

• Look for MCP server in client's server list
• Check if tools are listed in available tools
• Try a minimal test prompt (see below)

Step 5: Minimal Test Prompt

Use this minimal test prompt to verify tools are available:

Minimal Test Prompts

• "What MCP tools are available?" - Should list at least one tool from Corcava
• "List available MCP tools" - Should show tools like list_tasks, get_task, etc.
• "Show me my Corcava projects" - Should call list_projects tool and return results

Expected Response

If tools are working, you should see:

• List of available tools (list_tasks, get_task, create_task, etc.)
• Tool descriptions or capabilities
• Ability to actually call tools and get results

If Test Prompt Fails

If the test prompt doesn't work:

• Tools may still not be loaded (check restart steps above)
• Authentication may be failing silently (see Step 1)
• Server may not be selected correctly (see Step 2)

Step 6: Verify Server Initialization

Sometimes the server needs time to initialize or may be experiencing issues:

Server Health Check

Test Server Endpoint

curl -H "Authorization: Bearer YOUR_API_KEY" \
  https://app.corcava.com/mcp

This should return a tool list or valid response. If it returns an error or empty response, the server may be having issues.

Wait and Retry

Initialization Delay

After restarting your client, wait a few seconds for the MCP server connection to fully establish before testing tools.

Quick Fix Checklist

Systematic Troubleshooting

1. ✅ Tested API key with curl - does it return tools?
2. ✅ Verified server name and URL in config file
3. ✅ Cleared client cache (if applicable)
4. ✅ Fully quit and restarted MCP client
5. ✅ Waited a few seconds after restart
6. ✅ Tried minimal test prompt - do tools appear?
7. ✅ Checked client logs for error messages

Client-Specific Issues

Claude Desktop

If tools don't appear in Claude Desktop:

• See Claude Desktop troubleshooting
• Verify config file location and JSON validity
• Check Claude Desktop logs for errors

Cursor

If tools don't appear in Cursor:

• See Cursor troubleshooting
• Reload window after config changes
• Check Cursor MCP settings panel

Continue

If tools don't appear in Continue:

• See Continue SSE troubleshooting
• Verify SSE connection is established
• Check Continue extension logs

Still Not Working?

If you've tried all steps and tools still don't appear:

• Check client-specific troubleshooting guides (links above)
• Review 401 Unauthorized for auth issues
• See Connection Failed for network issues
• Check client logs for specific error messages
• Try creating a fresh API key and testing with that

Related Troubleshooting

• 401 Unauthorized - Fix authentication issues that prevent tools from loading
• Claude Desktop: Server Not Showing - Fix server not appearing in Claude Desktop
• Tool Calls Fail - Debug issues when tools are listed but calls fail
• Troubleshooting Index - Browse all troubleshooting guides