Genie UI MCP Server Connection Issue

[Bihaag_N]

Hi community,

I ran into an issue while connecting a third-party MCP server to Genie's general chat UI and wanted to check if anyone else has seen this.

The connection fails immediately during the initial MCP handshake with:

`TypeError: unhashable type: 'list'`

This happens before any query is even executed.

What's interesting is that the same MCP server works fine in Genie Code. The issue only seems to happen in the general chat UI.

From what I can tell, Genie general chat may be passing the raw MCP response directly into an internal handler without normalising certain fields first. Some third-party MCP servers return list-type values in places like tool manifests or OAuth scopes, and it looks like something downstream expects hashable types instead.

Has anyone else experienced this with external MCP servers, or found a cleaner fix/configuration on the connection side?

[Ashwin_DSA]

Hi @Bihaag_N,

From what I can gather, I couldn't find this exact TypeError: unhashable type: 'list' in the public docs, and I also don’t see any documented connection-side requirement stating that third-party MCP manifests need list fields normalised before Databricks can consume them.

What the public docs do confirm is that Databricks supports external MCP servers via managed proxies, that those servers must use the Streamable HTTP transport, and that they can be tested in Databricks-native surfaces like Genie Code and AI Playground. They also note that external MCP support depends on regions where Model Serving is available. Please take a look at Connect Genie Code to MCP servers and Install an external MCP server.

Given that the same server works in Genie Code but fails immediately during the initial handshake in general chat, this sounds more like a surface-specific product bug than a clean MCP connection misconfiguration. Since the failure happens before any actual tool call, the most useful next step is to capture a HAR from the general chat flow and file it with the initialise / tools-list payloads if you can. As a quick sanity check, I’d also test the same connection in AI Playground, since that’s explicitly documented as a supported way to validate external MCP integrations. Install an external MCP server.

If this answer resolves your question, could you mark it as “Accept as Solution”? That helps other users quickly find the correct fix.

[Bihaag_N]

Hi Ashwin,thank you for the prompt response.

So I did test the MCP server in the playground and it does work. However it still persists with that list error in Genie UI.

What's also weird is when I go to create an agent(supervisor agent) and ammend the MCP server connection as context it fails to pick up the MCP server.

Just to reiterate, I am using a remote MCP server(Power BI remote MCP server). It works perfectly on Genie code though.

Kind regards,

Bihaag

[Ashwin_DSA · Accepted solution]

Hi @Bihaag_N,

Thanks for checking. If the same remote Power BI MCP server works in both Genie Code and AI Playground, that strongly suggests the MCP server itself is properly configured, rather than a basic transport or auth issue with the remote server. Your latest note also adds that the same connection is not being picked up when you try to use it as context in a Supervisor Agent.

That lines up with the public docs, which say external MCP servers can be validated in AI Playground, used in Genie Code, and used programmatically in agents through the Databricks-managed proxy. See Install an external MCP server, Connect Genie Code to MCP servers, and Use external MCP servers in agents.

The Supervisor Agent docs also explicitly list the External MCP server as a supported tool / sub-agent type, with the key requirement being USE CONNECTION on the Unity Catalog connection. So if that permission is already in place and the connection still does not appear there, I would lean toward this being a surface-specific product issue in Genie UI/chat/agent selection, rather than something inherently unsupported about your remote MCP server.

So based on what you’ve shared, I think..

• The remote MCP server itself appears valid because it works in Genie Code and AI Playground
• The problem seems isolated to Genie UI and possibly the Supervisor Agent connection picker
• If permissions are correct, this looks more like a Databricks UI / product inconsistency than a connection-side fix for the Power BI MCP server

I’d recommend raising a support ticket and including..

• Confirmation that the same remote MCP works in Genie Code
• Confirmation that it also works in AI Playground
• Che exact TypeError: unhashable type: 'list' from Genie UI
• The fact that the connection also does not get picked up when added as Supervisor Agent context

If this answer resolves your question, could you mark it as “Accept as Solution”? That helps other users quickly find the correct fix.