I'm trying to connect my own MCP server via "mcp" type Tool. When testing connection via the built-in "List MCP Tools" button, it returns "error": "Failed to connect to MCP server: SSE error: Non-200 status code (500)". My MCP server logs however show a successful 200 response properly listing tools available in the MCP. I'm trying to find out if VAPI's MCP client is having issues (potentially alluded to by other users as well) or if it's an implementation problem on my end. Here's what I've tried: - Double checked that my server meets ALL of MCP's official and up-to-date guidelines "2025-03-26" - Attempted both outdated SSE and Streamable HTTP transport methods - Ran test scripts showing successful connection to MCP server and tool invocation What could be the issue here? tool_id: 60f5b001-2490-4037-adeb-b792f5e551fd https://cdn.discordapp.com/attachments/1369981378841542716/1369981379030421585/image.png?ex=681dd615&is=681c8495&hm=5b712c280a2aff2bc5aeaab9428f61955e3974f23e4025bd81526b75fa554de2&

It sounds like you've been thorough in your troubleshooting, and I can see you've already checked your server against the latest guidelines, tried different transport methods, and confirmed successful connections with test scripts. Since your server logs show a 200 response but Vapi is returning a 500 SSE error, it suggests there may be a mismatch in how the client and server are communicating, or possibly an issue with how the response is being interpreted by Vapi. Unfortunately, I don't have additional information available right now to pinpoint the exact cause of this error. If you have access to more detailed logs or error messages from either side, reviewing those might help narrow down the issue.

@Vapi Support Bot Would be great if I could get human input on this. I've carefully read Vapi's documentation on MCP integration (which is very lacking btw), Official MCP guidelines, AND I looked at Vapi's own MCP server repo. I've tried so much at this point that I just want to rule out the issue being on Vapi's end. Also btw (not related to my issue) there seems to be a bug in mcp tool creation via UI. When you enter your secret token and save the mcp tool, the token field gets reset to blank immediately. As a result there is no way to connect to Vapi's MCP server since you can't authenticate without your secret token.

I understand how frustrating it can be to run into these kinds of issues, especially after you've already done so much troubleshooting and research. At this time, I don't have any additional information or documentation available that addresses the SSE error 500 when connecting to your MCP server, nor details about the UI bug with the secret token field. I appreciate you sharing your experience and the steps you've taken so far.

Also - you clearly have duplicate instances of your support bot running. Put in some checks to allow only ONE instance at a time

Facing same issue too. I am using Zapier's MCP server and also tried my own MCP server. See the same 500 error. I hope @User prioritise this and have it resolved or provide a work around.

Following - having same issue

No MCP is working for me either, this has been working for a couple of weeks, the last two days it's completely broken, I have tried other industry standard servers as well and they don't work either.

hi @Shubham Bajaj @Kings_big💫 sorry to keep pinging you but seems like its system wide issue and would really appreciate your eye on this

We will investigate this issue and get back to you shortly

+1

Experiencing this for both Make & Zapier.

@Josh @Yassine @kevtae @fizgig @galoremate @SpriteCranberry Apologies for the delay. Let me take a look and get back to you guys. cc: @Kings_big💫 @kyle

Hiya @Shubham Bajaj , I know it's only been a day but are there any updates on the MCP connection issue? Has Vapi acknowledged or identified the issue? Thanks in advance.

We are doing some logs migration, so please wait for sometime.

This has been down for 5 days, we were going to demo this on Thurs. night to am AI tech group, it's going to be hard to recommend Vapi to clients if it goes down for almost a week at a time

The executives are working on it

@Kings_big💫 @Shubham Bajaj MCP is now working.. convey my thanks to your DEV team!

You're welcome

Hey @Kings_big💫 @Shubham Bajaj do you only support text/event-stream as transport method? From this documentation, the client is supposed to accept both application/json and text/event-stream https://modelcontextprotocol.io/specification/draft/basic/transports I have my server set up to return application/json but I'm getting this error after successful connection

"error": "Failed to connect to MCP server: SSE error: Invalid content type, expected \"text/event-stream\""

https://cdn.discordapp.com/attachments/1369981378841542716/1372335331365490738/image.png?ex=6826665f&is=682514df&hm=abb0aeb5ef8339d230adf9d3d9418a1365bef201bd5cfc5f2a67ecb4b5afa33e&

we only support

text/event-stream

.

Is it in roadmap to add application/json? I think use of SSE in MCP is slowly getting deprecated

Hey, Could you please schedule a brief call at your convenience so we can discuss this matter in detail? Kindly use the following link to book a suitable time: .

next available time is in a month 😅

Hey SpriteCraberry, You can raise an feature request for it over here: https://roadmap.vapi.ai