Error in Having Connection Issues while Making MCP in APIM

Issue Summary
Requests are reaching APIM, but fail with the error:

"reason": "ClientConnectionFailure", "message": "Client connection was unexpectedly closed.", "section": "outbound"
APIM Setup
SKU: v2 Premium

Network: VNet integrated with own subnet & NSG

Policies:

Inbound: Deny All (with allowed entries for devices and VNet)

Outbound: Deny All (with allowed entries for MCP backend APIs & devices)

APIM-to-APIM outbound: Explicitly Denied

Context
Using Expose REST API in API Management to act as MCP server. All relevant backend endpoints are allowed in outbound.

Suspected Cause
The MCP server process may perform internal APIM calls, which are currently blocked due to APIM-to-APIM outbound denial—this is the only restriction left.

Request
Please confirm if internal APIM calls are required by the MCP server process, and if so, advise on best practice to allow these secure.