Facing issue while accessing Expression Rule using MCP Server

Did you check any log files for details?

What is this expression doing? I fit uses other objects, make sure to check access for the service account to these other objects.

How are you testing the connection to the MCP exactly?

Also are you using the API Key to authenticate?

​@stefanhelzle0001, ​@mathieud0001 Thanks for your quick reply.

• My Expression Rule is very simple—it only returns a hard-coded string, "Holla".
• The MCP Server User Group has View permission for the Expression Rule, and the Service Account is a member of this group.
• The MCP client is also able to successfully connect to the Appian server. I can see the tools exposed by Appian in the MCP Inspector. However, the issue occurs when I try to invoke any of the tools.
• I am getting a 500 - Internal Server Error when calling the tools. I also checked the Appian logs, and they show an authentication error.

Logs:

Could this be related to the Service Account authentication or some additional permission/configuration required for invoking the MCP tools?

Any suggestions on what I should check would be greatly appreciated.

That AuthorizationException looks more like a platform role issue than object security  worth checking whether the service account is actually assigned the Designer role, since Viewer on the rule alone isn't enough.

​@stephane.kamga Thanks a lot for the quick reply.

I tried adding the Service Account to the Designer role as well, but I am still getting the error.

However, after assigning the Designer role, the error seems to have changed. It now appears to be related to the Designer.

Could you please take a look and let me know if I am missing any additional configuration or permissions?

Thanks again for your help.

Hello Everyone,

Has anyone successfully used the MCP Server functionality? Is it working for anyone else?

I would appreciate it if you could share experience or any insights you may have.

Thanks in advance for your help and valuable input.

Regards,

Try

• Go to Admin Console → Users.
• Open the Service Account.
• Assign it the Designer platform role.
• Confirm it remains in the MCP Server User Group.
• Verify that group has Viewer access to the Expression Rule and any dependent objects.
• Reconnect MCP Inspector using the Service Account’s API key, then invoke the tool again.

​@stefanhelzle0001 ​@mathieud0001  ​@stephane.kamga  ​@naresht804249 Thank you all for your inputs and suggestions.

The same changes are working as expected in the Test environment. I will investigate further and, if I find anything interesting or relevant, I will update it here.

Note: As suggested by ​@stephane.kamga and ​@naresht804249, the Designer role is required for the Service Account. I believe this requirement is missing from the Appian documentation.

Thanks & Regards,