adding MCP server to OpenAI Tools not working

[Telemarker77]

I've been trying for hours to get AOpenAI "playground to simply connect to my NLWeb MCP server (default).

I am using the mcp_handler.py code that is on the microsoft/NLWeb repo.

OpenAI sends this :
{ "jsonrpc": "2.0", "method": "initialize", "id": 1, "params": { "protocolVersion": "2025-03-26", "capabilities": {}, "clientInfo": { "name": "openai-mcp", "version": "1.0.0" } } }

and the NLWeb server sends back :

400

{ "type": "function_response", "status": "error", "error": "Unknown function: None" }

and this was my terminal output:

2025-07-03 05:59:00,664 - core.mcp_handler - ERROR - logger:151 - Empty MCP request body Empty MCP request body 2025-07-03 05:59:03,648 - core.mcp_handler - ERROR - logger:151 - Empty MCP request body Empty MCP request body 2025-07-03 05:59:07,319 - core.mcp_handler - ERROR - logger:151 - Empty MCP request body Empty MCP request body 2025-07-03 05:59:13,021 - core.mcp_handler - ERROR - logger:151 - Empty MCP request body Empty MCP request body 2025-07-03 05:59:15,598 - core.mcp_handler - ERROR - logger:151 - Empty MCP request body Empty MCP request body 2025-07-03 05:59:18,381 - core.mcp_handler - ERROR - logger:151 - Empty MCP request body Empty MCP request body 2025-07-03 05:59:22,465 - core.mcp_handler - ERROR - logger:151 - Empty MCP request body Empty MCP request body 2025-07-03 05:59:28,300 - core.mcp_handler - ERROR - logger:151 - Empty MCP request body Empty MCP request body

WHne I use the /static/mcp_test.html tool it works fine:

POST/mcp
{
"function_call": {
"name": "ask",
"arguments": "{"query":"I have a really bad headache","query_id":"query_1751522226795_k82oehe6j"}"
}
}

200 response with expected payload:

{
"type": "function_response",
"status": "success",
"response": {
"asking_sites": {
"message": "Asking Medicines, Healthdirect, Pregnancy-birth-and-baby"
},
"results": [
{
"url": "https://headacheaustralia.org.au/",
"name": "",
"site": "Partner-Website",
"siteUrl": "Partner-Website",
"score": 85,
"description": "Migraine and Headache Australia is an organization dedicated to providing information and support related to headaches and migraines.",
"schema_object": {
"url": "https://headacheaustral....

[FrancesDrake]

Hi, I'm currently doing some experiments with NLWeb in combination with agentic systems. I also got the same 400 response with the "Empty MCP request body" in the logs. I'm currently using the local setup (running app-file.py) and trying to connect via http://localhost:8000/mcp. Like for my other MCP Servers, for testing I use the mcp-inspector. It seems like the current implementation is not working for MCP using streamable-http or server-side-events.

[rvguha]

Please try #256 (this is post refactoring). I tested this with MCP Inspector and it seems to work.

…

On Fri, Jul 4, 2025 at 6:29 AM Frank Holzwarth ***@***.***> wrote: *FrancesDrake* left a comment (nlweb-ai/NLWeb#255) <#255 (comment)> Hi, I'm currently doing some experiments with NLWeb in combination with agentic systems. I also got the same 400 response with the "Empty MCP request body" in the logs. I'm currently using the local setup (running app-file.py) and trying to connect via http://localhost:8000/mcp. Like for my other MCP Servers, for testing I use the mcp-inspector <https://github.com/modelcontextprotocol/inspector>. It seems like the current implementation is not working for MCP using streamable-http or server-side-events. — Reply to this email directly, view it on GitHub <#255 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABICKCVZ43VFUCMSSQKBXYD3GZ6TBAVCNFSM6AAAAACAVZFKE6VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTAMZWGI4DOMRUHE> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[FrancesDrake]

Hi @rvguha, thank you for your quick response! I was able to integrate the PR #256 mentioned refactor-step-2 branch into my setup. Indeed I can now access the /mcp endpoint, calling the tools successfully! I will now build on top of this branch for proceeding with my experiments/integrations (also with my cloud infra). As it looks like a bigger refactoring, I will try to merge changes frequently into mine, possibly giving feedback there.

[rvguha]

Thank you. Hopefully, this will be the last of the major refactorings ...

…

On Mon, Jul 7, 2025 at 1:45 AM Frank Holzwarth ***@***.***> wrote: *FrancesDrake* left a comment (nlweb-ai/NLWeb#255) <#255 (comment)> Hi @rvguha <https://github.com/rvguha>, thank you for your quick response! I was able to integrate the PR #256 <#256> mentioned refactor-step-2 branch <https://github.com/microsoft/NLWeb/tree/refactor-step-2> into my setup. Indeed I can now access the /mcp endpoint, calling the tools successfully! I will now build on top of this branch for proceeding with my experiments/integrations (also with my cloud infra). As it looks like a bigger refactoring, I will try to merge changes frequently into mine, possibly giving feedback there. — Reply to this email directly, view it on GitHub <#255 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABICKCR7R7QZUF6DMDENYOD3HIXQ5AVCNFSM6AAAAACAVZFKE6VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTANBUGAYTKNRYGU> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[rvguha]

Telemarker77, can you pull in #256 and try again?

[genericrobot77]

I synced to the microsoft/NLWeb repo yesterday so I'm assuming I should now have the refactored code in there.
@rvguha what MCP inspector are you using ? is it https://modelcontextprotocol.io/docs/tools/inspector

if so are you able to share the configuration that works for you? I'm having trouble working out how to add my mcp end point to this inspector

[rvguha]

i am using https://github.com/modelcontextprotocol/inspector

The refactored code is not yet in main. We are still testing it. It will hopefully be in main by this time tomorrow

[FrancesDrake]

Hi @rvguha, thank you for bringing the changes to the main branch! I fetch frequently for new changes and I was able to integrate the current NLWeb via Docker/K8s to my cloud infrastructure. The /ask endpoint is working perfectly fine, with the /mcp endpoint I got unfortunately some challenges still. As the mcp-inspector is working, I'm now trying to connect against "real" agentic systems. There I'm facing errors, as I can't establish a connection on startup. I'm getting following error via the MCP connection: TypeError: fetch failed, in the logs of NLWeb Server I can't see errors, only "normal" MCP requests in the logs.

The following setups I'm using for testing. For reproducibility I was also trying the locahost setup. And I was trying to connect to seperate MCP servers (Github, Jira, Azure) on my platform, which were successfully establishing a connection.

GitHub Copilot

With .vscode/mcp.json I was trying to connect to both cloud and localhost, both were failing. The mcp.json content:

{
  "inputs": [
    {
      "type": "promptString",
      "id": "ai-platform-mcp-key",
      "description": "Access Key for MCP servers",
      "password": true
    }
  ],
  "servers": {
    "nlweb-local": {
      "url": "http://localhost:8000/mcp",
      "type": "http"
    },
    "nlweb-cloud": {
      "url": "http://nlweb.my.domain.com/mcp",
      "type": "http",
      "headers": {
          "Authorization": "Bearer ${input:ai-platform-mcp-key}"
      }
    }
  }
}

Eclipse Theia

As my cloud infrastructure is containing a Eclipse Theia instance with MCP capabilities, I was trying to connect to the cloud hosted NLWeb MCP server. There also the connection startup got rejected.

Langgraph

I was also using this tutorial to verify the other used tooling. Both tested local and cloud, both are also unfortunatly not connecting on startup.

[rvguha]

How are you trying to connect to it?

…

On Wed, Jul 16, 2025 at 9:40 AM Frank Holzwarth ***@***.***> wrote: *FrancesDrake* left a comment (nlweb-ai/NLWeb#255) <#255 (comment)> Hi @rvguha <https://github.com/rvguha>, thank you for bringing the changes to the main branch! I fetch frequently for new changes and I was able to integrate the current NLWeb via Docker/K8s to my cloud infrastructure. The /ask endpoint is working perfectly fine, with the /mcp endpoint I got unfortunately some challenges still. As the mcp-inspector <https://github.com/modelcontextprotocol/inspector> is working, I'm now trying to connect against "real" agentic systems. There I'm facing errors, as I can't establish a connection on startup. I'm getting following error via the MCP connection: TypeError: fetch failed, in the logs of NLWeb Server I can't see errors, only "normal" MCP requests in the logs. The following setups I'm using for testing. For reproducibility I was also trying the locahost setup. And I was trying to connect to seperate MCP servers (Github, Jira, Azure) on my platform, which were successfully establishing a connection. GitHub Copilot With .vscode/mcp.json I was trying to connect to both cloud and localhost, both were failing. The mcp.json content: { "inputs": [ { "type": "promptString", "id": "ai-platform-mcp-key", "description": "Access Key for MCP servers", "password": true } ], "servers": { "nlweb-local": { "url": "http://localhost:8000/mcp", "type": "http" }, "nlweb-cloud": { "url": "http://nlweb.my.domain.com/mcp", "type": "http", "headers": { "Authorization": "Bearer ${input:ai-platform-mcp-key}" } } } } Eclipse Theia As my cloud infrastructure is containing a Eclipse Theia <https://github.com/eclipse-theia/theia>instance with MCP capabilities <https://eclipsesource.com/blogs/2024/12/19/theia-ide-and-theia-ai-support-mcp/>, I was trying to connect to the cloud hosted NLWeb MCP server. There also the connection startup got rejected. Langgraph I was also using this tutorial <https://composio.dev/blog/langchain-mcp-adapter-a-step-by-step-guide-to-build-mcp-agents> to verify the other used tooling. Both tested local and cloud, both are also unfortunatly not connecting on startup. — Reply to this email directly, view it on GitHub <#255 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABICKCWBYTV7IZG2WTQ3R233IZ565AVCNFSM6AAAAACAVZFKE6VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTANZZGQYDSMZZGU> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[FrancesDrake]

Hi, I was using the default MCP mechanism of the tools connecting to the NLWeb server. Some more information:

GitHub Copilot

Setting up the above described .vscode/mcp.json in the workspace, then activating it via the file (Start button right over the MCP server entries) or the Command Palette (MCP: List Servers > nlweb-cloud > Start Server). I’m following mainly this instructions. There I see the above mentioned error in the logs.

Eclipse Theia

As described in the article, there is a configuration that is added to the settings.json. After adding the MCP server, it can be connected via the UI and then used by the integrated Agents of Theia. There I got a different error, but this is most likely related to Theia MCP SSE backup mechanism.

Langgraph

I was adjusting the script in the tutorial with the NLWeb MCP server and Azure OpenAI objects, then just starting it via the node command. There it fails on connect (other MCP servers are not affected).