logic app standard BYO MCP is failing with The connection for MCP tool 'mcpclient-2' is missing.

[Xiaoyu-Huang]

Severity

P1 - Critical (Blocking production)

Describe the Bug with repro steps

BYO MCP in logic app should work with proper authentication. now it is failing with below error. even I tried to create new connection, it is still failing with same
{
"error": {
"code": "InvalidActionToolMcpConnection",
"message": "The connection for MCP tool 'mcpclient-2' is missing."
}
}

I switched to old designer, and it works

What type of Logic App Is this happening in?

Standard (Portal)

Are you experiencing a regression?

No response

Which operating system are you using?

Windows

Did you refer to the TSG before filing this issue? https://aka.ms/lauxtsg

Yes

Workflow JSON

{
    "definition": {
        "$schema": "https://schema.management.azure.com/providers/Microsoft.Logic/schemas/2016-06-01/workflowdefinition.json#",
        "contentVersion": "1.0.0.0",
        "actions": {
            "Agent": {
                "type": "Agent",
                "inputs": {
                    "parameters": {
                        "deploymentId": "gpt-4o-mini",
                        "messages": [
                            {
                                "role": "system",
                                "content": "you are expert of IcM ecosystem. You could leverage icm mcp server to get to know icm knowledge"
                            },
                            {
                                "role": "user",
                                "content": "what is the team public id for icm team Incident Automation DRI"
                            }
                        ],
                        "agentModelType": "AzureOpenAI",
                        "agentModelSettings": {
                            "agentHistoryReductionSettings": {
                                "agentHistoryReductionType": "maximumTokenCountReduction",
                                "maximumTokenCount": 128000
                            },
                            "deploymentModelProperties": {
                                "name": "gpt-4.1",
                                "format": "OpenAI",
                                "version": "2025-06-10"
                            }
                        }
                    },
                    "modelConfigurations": {
                        "model1": {
                            "referenceName": "agent"
                        }
                    }
                },
                "tools": {
                    "Add_new_MCP_server": {
                        "type": "McpClientTool",
                        "kind": "Builtin",
                        "inputs": {
                            "parameters": {
                                "allowedTools": [
                                    "get_teams_by_public_id",
                                    "get_teams_by_name",
                                    "get_team_by_id"
                                ]
                            },
                            "connectionReference": {
                                "connectionName": "mcpclient-2"
                            }
                        }
                    }
                },
                "runAfter": {},
                "limit": {
                    "count": 100
                }
            }
        },
        "outputs": {},
        "triggers": {
            "When_an_HTTP_request_is_received": {
                "type": "Request",
                "kind": "Http"
            }
        }
    },
    "kind": "stateful"
}

Screenshots or Videos

No response

Environment

Browser: edge

Additional context

No response

[github-actions]

AI Triage Analysis

Component: Agentic / MCP Connection Serialization | Priority: P1 | SKU: Standard (Portal)

Relevant Code

• libs/designer/src/lib/core/actions/bjsworkflow/connections.ts:515-528 — getConnectionsApiAndMapping reconstructs built-in MCP connections only from inline inputs.Connection.McpServerUrl format; does not handle the connectionReference.connectionName format used in Agent tools
• libs/designer/src/lib/core/actions/bjsworkflow/connections.ts:764-765 — McpConnection reference key is read from inputs.connectionReference.connectionName, so the mapping is built, but the corresponding ConnectionReference object may not be initialized in the store
• libs/logic-apps-shared/src/designer-client-services/lib/standard/connection.ts:125-156 — AgentMcpConnectionModel / agentMcpConnections in ConnectionsData is the storage location for BYO MCP connections in connections.json
• libs/designer/src/lib/core/mcp/utils/serializer.ts:248-266 — MCP connections are persisted only if they have an ARM resource ID; non-ARM BYO connections may be skipped
• libs/designer/src/lib/core/parsers/BJSWorkflow/BJSDeserializer.ts:734-756 — McpClient tools inside Agent.tools are added to allActions and therefore processed, but connection references may not be re-registered correctly

Probable Root Cause

When a McpClientTool inside an Agent.tools block references a connection via connectionReference.connectionName, the designer likely fails to persist that connection into the agentMcpConnections section of connections.json when saving the workflow. The backend runtime then cannot resolve mcpclient-2 and returns InvalidActionToolMcpConnection. The reporter confirms the error persists even after creating a new connection, suggesting the issue is in the save/serialize path rather than just the load path. The getConnectionsDataToSerialize logic in libs/designer/src/lib/core/mcp/utils/serializer.ts may only process connections with ARM IDs, dropping BYO connections that don't have them.

Suggested Investigation

1. Verify whether after saving the workflow through the designer, connections.json contains an agentMcpConnections["mcpclient-2"] entry with the correct mcpServerUrl and authentication fields.
2. Check getConnectionsDataToSerialize and changeConnectionMappingsForNodes to confirm McpClientTool nodes inside Agent.tools correctly populate connectionsMapping and connectionReferences in the Redux store upon connection creation.
3. Inspect whether updateMcpConnection is dispatched with the correct nodeIds for Agent-nested tools when the user creates or edits the connection in the designer.

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Calibration: reviewed 5 past triages, 0 corrections identified.

Generated by Issue Triage Agent for Azure Logic Apps UX for issue #9006 · ◷