Feature Request: HTTP Headers Support for SSE MCP Server Configuration

[jescarri]

Hello, thanks for this slackbot it works great, I would like to request the feature to allow passing extra headers to the SSE endpoint configuration.

Summary

Currently, the SSE endpoint configuration lacks support for custom HTTP headers, which limits our ability to authenticate with MCP servers that require header-based authentication (e.g., Bearer tokens, API keys, custom auth headers).

Background

Many production MCP servers implement authentication mechanisms that rely on HTTP headers for security. Without the ability to configure custom headers in our SSE transport, we cannot connect to these authenticated endpoints, limiting the client's utility in enterprise environments.

Proposed Solution

Add an httpHeaders field to the MCPServerConfig structure that allows users to specify custom HTTP headers for SSE connections:

servers:
  - name: "authenticated-server"
    command: null
    transport:
      type: "sse"
      url: "https://api.example.com/mcp/sse"
    httpHeaders:
      Authorization: "Bearer ${API_TOKEN}"
      X-API-Key: "${API_KEY}"

Technical Considerations

• Support environment variable substitution in header values for secure credential management
• Ensure headers are properly passed through reconnection logic
• Maintain backward compatibility with existing configurations
• Consider security implications and avoid logging sensitive header values

Use Cases

• Connecting to MCP servers behind API gateways requiring authentication
• Integration with enterprise services using custom authentication headers
• Supporting various auth patterns (Bearer tokens, API keys, custom schemes)

Priority

This would significantly expand the client's compatibility with production MCP deployments and is a common requirement in enterprise environments.