Connection Error - Check if your MCP server is running and proxy token is correct

[marksmith-II]

Hi,

I'm creating an issue similar to #724 .

I've tried all of the recommendations in issue #724 with the same connection issue. Below is my code for my mcp_server.py.

I'm unable to progress in the tutorial at this point in time.

Any help would be greatly appreciated.

mcp.server.py*

from pydantic import Field # type: ignore
from mcp.server.fastmcp import FastMCP # type: ignore

mcp = FastMCP("DocumentMCP", log_level="ERROR")

docs = {
"deposition.md": "This deposition covers the testimony of Angela Smith, P.E.",
"report.pdf": "The report details the state of a 20m condenser tower.",
"financials.docx": "These financials outline the project's budget and expenditures.",
"outlook.pdf": "This document presents the projected future performance of the system.",
"plan.md": "The plan outlines the steps for the project's implementation.",
"spec.txt": "These specifications define the technical requirements for the equipment.",
}

@mcp.tool(
name="read_doc_contents",
description="Reads the contents of a specified document and returns it as a string.",
)
def read_document(
doc_id: str = Field(description="The ID of the document to read."),
):

if doc_id not in docs:
    raise ValueError(f"Document with ID '{doc_id}' not found.")
return docs[doc_id] 

@mcp.tool(
name="edit_document",
description="Edits the contents of a specified document with new content.",
)
def edit_document(
doc_id: str = Field(description="The ID of the document to edit."),
old_str: str = Field(description="The string to be replaced in the document."),
new_str: str = Field(description="The new content to write into the document."),
):
if doc_id not in docs:
raise ValueError(f"Document with ID '{doc_id}' not found.")
docs[doc_id] = docs[doc_id].replace(old_str, new_str)
return f"Document '{doc_id}' has been updated."

TODO: Write a resource to return all doc id's

TODO: Write a resource to return the contents of a particular doc

TODO: Write a prompt to rewrite a doc in markdown format

TODO: Write a prompt to summarize a doc

if name == "main":
mcp.run(transport="stdio")

[kumarshantanu]

MCP Inspector needs to verbosely print (the reason) what was it expecting from the server and what did it find instead.

I have frequently run into this issue in MCP Inspector even when the MCP server is up, maybe with a bit of incorrect protocol implementation (in my MCP server) that I am trying to debug using MCP Inspector.

[sdelamo]

For met the issue was a server error in the logging/setLevel request.