"New Foundry" Portal adding a Custom MCP Remote Server. I get an error stating type "custom_MCP" is invalid, that only "mcp" is valid.

[Mazecreator]

Technical Feedback

Describe the precise feedback.
I am using the "New Foundry" Portal and adding a Custom MCP Remote Server. I get an error stating type "custom_MCP" is invalid, that only "mcp" is valid. It appears the Foundry Portal is creating an extra "Type" in the agent definition:

metadata:
description: ""
modified_at: "1765337294"
object: agent.version
id: Agent-for-Project1:7
name: Agent-for-Project1
version: "7"
description: ""
created_at: 1765337294
definition:
kind: prompt
model: gpt-4o
instructions: You are a helpful agent used to load files into the system.
tools:
- type: custom_MCP
- type: mcp
server_label: MCP_Agent
server_url: https://XXXXXXXXX.azure-api.net/v1/directive
allowed_tools:

Is this a known issue? I am using BICEP to deploy the Foundry resource; is there a preview version I need to use or something else I am doing wrong? I am using BYO VNET binding as well as the non-preview latest version of the resource 2025-09-01.

Desired Outcome

Describe the desired outcome.
The New Foundry Tool connection should be properly adding the Custom MCP Server for use by the Agents.

Current Workaround

Describe the current workaround.
Looking into using Python to push in the configuration for now

[leestott]

Hi, The portal is incorrectly injecting an extra type: custom_MCP entry into the agent definition, even though the backend only accepts type: mcp. This causes schema validation to fail when the agent is saved or executed. The issue is confirmed in the GitHub thread you surfaced.

The New Foundry Portal UI is generating an invalid agent definition:

tools:
  - type: custom_MCP   # invalid
  - type: mcp          # valid

The backend schema only accepts:

type: mcp

The portal should not be adding custom_MCP at all. This is a UI‑side bug, not a BICEP, VNET, or API-version issue.

• BICEP deployment does not influence how the portal serialises the agent definition.
• API version 2025‑09‑01 is the correct non-preview version and is not the cause.
• BYO VNET binding does not affect tool schema generation.
• The issue occurs only when using the new Portal UI to add a Custom MCP server.

Desired Outcome
We want the portal to generate:

tools:
  - type: mcp
    server_label: MCP_Agent
    server_url: https://XXXXXXXXX.azure-api.net/v1/directive
    allowed_tools: [...]

This is the correct and expected structure.

Current Workaround (Validated)

using Python to push the MCP tool configuration is currently the only reliable method.

Python or direct REST API calls correctly produce:

- type: mcp

…without the invalid custom_MCP entry.

• No preview API version resolves this.
• No portal fix has been released yet.

Recommended Path Forward (Until Fix Arrives)

Continue using Python or REST to define MCP tools

This ensures the agent definition is valid.

Avoid editing MCP tool definitions in the Portal

Any edit triggers the portal to re‑serialize the definition and re‑insert the invalid custom_MCP.

##Keep your BICEP deployment as-is
There’s nothing wrong with your template or API version.

##Clean, Valid MCP Agent Definition (No custom_MCP )

  object: agent.version
  id: Agent-for-Project1:7
  name: Agent-for-Project1
  version: "7"
  description: ""
  created_at: 1765337294
  modified_at: 1765337294

definition:
  kind: prompt
  model: gpt-4o
  instructions: |
    You are a helpful agent used to load files into the system.

  tools:
    - type: mcp
      server_label: MCP_Agent
      server_url: https://XXXXXXXXX.azure-api.net/v1/directive
      allowed_tools:
        - list_tools
        - call_tool
        - get_capabilities
        # Add any additional MCP tool names here