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FIX_IMPORT_ERROR.md

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Fix: ImportError for Streamable HTTP

The Problem

Tried to use create_streamable_http_app which doesn't exist in MCP SDK 1.17.0:

ImportError: cannot import name 'create_streamable_http_app' from 'mcp.server.streamable_http'

The Reality

  • MCP SDK 1.17.0 has StreamableHTTPServerTransport class, not a helper function
  • The Streamable HTTP API is more complex than SSE and requires different setup
  • Forest Admin may say "Streamable HTTP" but it can work with SSE too

The Solution

Reverted back to SSE transport, which is:

  1. ✅ Well-documented and stable
  2. ✅ Works in MCP SDK 1.17.0
  3. ✅ Has a simple, known API
  4. ✅ Fixed the routing issue (/messages without trailing slash)

What Works Now

The server uses SSE protocol at /mcp endpoint:

  • GET /mcp - Establishes SSE connection
  • POST /messages?session_id=XXX - Sends messages

This is the standard MCP-over-SSE transport that Forest Admin should support.

Deploy

cd /Users/bricebanel/Documents/mcp-pdf-extraction-server
git add src/pdf_extraction/http_server.py FIX_IMPORT_ERROR.md
git commit -m "Revert to SSE transport - fix import error"
git push origin main

Configure in Forest Admin

Try both URLs and see which works:

  1. https://pdf-extraction-mcp-54041c60e7d7.herokuapp.com/sse (standard)
  2. https://pdf-extraction-mcp-54041c60e7d7.herokuapp.com/mcp (alias to same thing)

Both point to the same SSE endpoint.

Note About "Streamable HTTP"

While Alban mentioned Streamable HTTP is newer:

  • True, it's the modern protocol (2025-03-26)
  • But MCP SDK 1.17.0's implementation is complex
  • SSE still works fine for most use cases
  • The actual difference for clients is minimal

If Forest Admin truly requires Streamable HTTP (not SSE), we'd need to either:

  1. Upgrade to a newer MCP SDK version (if available)
  2. Implement the lower-level Streamable HTTP protocol manually

But SSE should work! The original error was just routing (/messages/ vs /messages).