Server crashes with "Server does not support completions" error on startup

Firecrawl MCP Server Crashing with "Server does not support completions"

Users reported that the firecrawl-mcp server was crashing immediately upon startup with the error message "Server does not support completions (required for completion/complete)". This prevented the server from functioning as an MCP server with clients like Claude Code/Claude Desktop.

Problem Details

Package: firecrawl-mcp
Error: Error: Server does not support completions (required for completion/complete)
Client: Claude Code CLI or Claude Desktop
Platform: macOS (reported, but likely affects other platforms)

The issue manifested when attempting to connect to the MCP server after configuring it. The server would fail to start, rendering it unusable.

Root Cause

The root cause was traced to an incompatibility between the modelcontextprotocol/sdk dependency and the firecrawl-mcp server. Specifically, version 1.22 of the SDK was being installed (even though package-lock.json specified v1.18), which introduced a requirement for completion support that the firecrawl-mcp server wasn't yet fully implementing. This led to the server crashing during initialization when the MCP client attempted to use completion-related features.

Solution

The firecrawl-mcp maintainers quickly identified and addressed the issue by pinning the modelcontextprotocol/sdk dependency to version 1.18 in their internal fork of fastmcp. This ensured that a compatible version of the SDK was used, resolving the completion support requirement and allowing the server to start successfully.

To resolve the issue, users needed to reinstall the firecrawl-mcp package. Here's how you can do it:

Uninstall the existing package: If you installed it globally:
```
npm uninstall -g firecrawl-mcp
```
Or, if installed locally within a project:
```
npm uninstall firecrawl-mcp
```
Clear the npm cache: This step is optional, but can ensure that you're getting the latest version:
```
npm cache clean --force
```
Reinstall the package: Use the same method you used previously. For global installation:
```
npm install -g firecrawl-mcp
```
Or, for local installation:
```
npm install firecrawl-mcp
```
If you are using npx, you can reinstall and run the server in one step:
```
npx -y firecrawl-mcp
```

After reinstalling the package (version 3.6.1 or later), the server should start without the "Server does not support completions" error.

Additional Considerations

Version Compatibility: Always ensure that your firecrawl-mcp version is compatible with the MCP client you are using (e.g., Claude Code, Claude Desktop, VSCode). Refer to the official documentation for recommended versions.
Dependency Management: This incident highlights the importance of carefully managing dependencies in your projects. Using package-lock.json or similar mechanisms can help ensure consistent and reproducible builds.
Stay Updated: Keep your firecrawl-mcp package up-to-date to benefit from bug fixes and new features.