fix: AI connection type propagation and get_node improvements (v2.28.1)

Bug fixes:
- Issue #458: addConnection now preserves AI connection types (ai_tool, ai_memory, ai_languageModel) instead of defaulting to 'main'
- Fixed false positive "AI Agent has no tools connected" validation warning

Enhancements:
- Added expectedFormat field to resourceLocator properties in get_node output
- Added versionNotice field to make typeVersion more prominent

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,57 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.28.1] - 2025-12-01
+
+### 🐛 Bug Fixes
+
+**Issue #458: AI Connection Type Propagation**
+
+Fixed `addConnection` operation in workflow diff engine defaulting `targetInput` to "main" instead of preserving the source output type. This caused AI tool connections to be created with incorrect type.
+
+- **Root Cause**: `targetInput` defaulted to `'main'` regardless of `sourceOutput` type
+- **Fix**: Changed default to `sourceOutput` to preserve connection type (ai_tool, ai_memory, ai_languageModel)
+- **Files**: `src/services/workflow-diff-engine.ts:760`
+
+**AI Agent Validation False Positive**
+
+Fixed false positive "AI Agent has no tools connected" warning when tools were properly connected.
+
+- **Root Cause**: Validation checked connections FROM agent instead of TO agent
+- **Fix**: Search all connections where target node is the agent
+- **Files**: `src/services/workflow-validator.ts:1148-1163`
+
+### ✨ Enhancements
+
+**get_node: expectedFormat for resourceLocator Properties**
+
+Added `expectedFormat` field to resourceLocator properties in `get_node` output. This helps AI models understand the correct format for these complex property types.
+
+```json
+{
+  "name": "model",
+  "type": "resourceLocator",
+  "expectedFormat": {
+    "structure": { "mode": "string", "value": "string" },
+    "modes": ["list", "id"],
+    "example": { "mode": "id", "value": "gpt-4o-mini" }
+  }
+}
+```
+
+**get_node: versionNotice Field**
+
+Added `versionNotice` field to make typeVersion more prominent in get_node output, reducing the chance of AI models using outdated versions.
+
+```json
+{
+  "version": "1.3",
+  "versionNotice": "⚠️ Use typeVersion: 1.3 when creating this node"
+}
+```
+
+**Conceived by Romuald Członkowski - [AiAdvisors](https://www.aiadvisors.pl/en)**
+
 ## [2.28.0] - 2025-12-01
 
 ### ✨ Features

package.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp",
-  "version": "2.28.0",
+  "version": "2.28.1",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

src/mcp/server.ts

@@ -2203,14 +2203,19 @@ Full documentation is being prepared. For now, use get_node_essentials for confi
     // Get operations (already parsed by repository)
     const operations = node.operations || [];
     
+    // Get the latest version - this is important for AI to use correct typeVersion
+    const latestVersion = node.version ?? '1';
+
     const result = {
       nodeType: node.nodeType,
       workflowNodeType: getWorkflowNodeType(node.package ?? 'n8n-nodes-base', node.nodeType),
       displayName: node.displayName,
       description: node.description,
       category: node.category,
-      version: node.version ?? '1',
+      version: latestVersion,
       isVersioned: node.isVersioned ?? false,
+      // Prominent warning to use the correct typeVersion
+      versionNotice: `⚠️ Use typeVersion: ${latestVersion} when creating this node`,
       requiredProperties: essentials.required,
       commonProperties: essentials.common,
       operations: operations.map((op: any) => ({

src/services/property-filter.ts

@@ -16,6 +16,11 @@ export interface SimplifiedProperty {
   placeholder?: string;
   showWhen?: Record<string, any>;
   usageHint?: string;
+  expectedFormat?: {
+    structure: Record<string, string>;
+    modes?: string[];
+    example: Record<string, any>;
+  };
 }
 
 export interface EssentialConfig {
@@ -322,7 +327,18 @@ export class PropertyFilter {
         };
       });
     }
-    
+
+    // Add expectedFormat for resourceLocator types - critical for correct configuration
+    if (prop.type === 'resourceLocator') {
+      const modes = prop.modes?.map((m: any) => m.name || m) || ['list', 'id'];
+      const defaultValue = prop.default?.value || 'your-resource-id';
+      simplified.expectedFormat = {
+        structure: { mode: 'string', value: 'string' },
+        modes,
+        example: { mode: 'id', value: defaultValue }
+      };
+    }
+
     // Include simple display conditions (max 2 conditions)
     if (prop.displayOptions?.show) {
       const conditions = Object.keys(prop.displayOptions.show);

src/services/workflow-diff-engine.ts

@@ -757,7 +757,8 @@ export class WorkflowDiffEngine {
     const { sourceOutput, sourceIndex } = this.resolveSmartParameters(workflow, operation);
 
     // Use nullish coalescing to properly handle explicit 0 values
-    const targetInput = operation.targetInput ?? 'main';
+    // Default targetInput to sourceOutput to preserve connection type for AI connections (ai_tool, ai_memory, etc.)
+    const targetInput = operation.targetInput ?? sourceOutput;
     const targetIndex = operation.targetIndex ?? 0;
 
     // Initialize source node connections object

src/services/workflow-validator.ts

@@ -1137,16 +1137,23 @@ export class WorkflowValidator {
     }
 
     // Check for AI Agent workflows
-    const aiAgentNodes = workflow.nodes.filter(n => 
+    const aiAgentNodes = workflow.nodes.filter(n =>
-      n.type.toLowerCase().includes('agent') || 
+      n.type.toLowerCase().includes('agent') ||
       n.type.includes('langchain.agent')
     );
-    
+
     if (aiAgentNodes.length > 0) {
       // Check if AI agents have tools connected
+      // Tools connect TO the agent, so we need to find connections where the target is the agent
       for (const agentNode of aiAgentNodes) {
-        const connections = workflow.connections[agentNode.name];
+        // Search all connections to find ones targeting this agent via ai_tool
-        if (!connections?.ai_tool || connections.ai_tool.flat().filter(c => c).length === 0) {
+        const hasToolConnected = Object.values(workflow.connections).some(sourceOutputs => {
+          const aiToolConnections = sourceOutputs.ai_tool;
+          if (!aiToolConnections) return false;
+          return aiToolConnections.flat().some(conn => conn && conn.node === agentNode.name);
+        });
+
+        if (!hasToolConnected) {
           result.warnings.push({
             type: 'warning',
             nodeId: agentNode.id,

tests/unit/services/workflow-diff-engine.test.ts

@@ -4665,4 +4665,223 @@ describe('WorkflowDiffEngine', () => {
       expect(result.errors![0].message).toContain('executeWorkflowTrigger cannot activate workflows');
     });
   });
+
+  // Issue #458: AI connection type propagation
+  describe('AI Connection Type Propagation (Issue #458)', () => {
+    it('should propagate ai_tool connection type when targetInput is not specified', async () => {
+      const workflowWithAI = {
+        ...baseWorkflow,
+        nodes: [
+          {
+            id: 'agent1',
+            name: 'AI Agent',
+            type: '@n8n/n8n-nodes-langchain.agent',
+            typeVersion: 2.1,
+            position: [500, 300] as [number, number],
+            parameters: {}
+          },
+          {
+            id: 'tool1',
+            name: 'Calculator',
+            type: '@n8n/n8n-nodes-langchain.toolCalculator',
+            typeVersion: 1,
+            position: [300, 400] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const operation: AddConnectionOperation = {
+        type: 'addConnection',
+        source: 'Calculator',
+        target: 'AI Agent',
+        sourceOutput: 'ai_tool'
+        // targetInput not specified - should default to sourceOutput ('ai_tool')
+      };
+
+      const request: WorkflowDiffRequest = {
+        id: 'test-workflow',
+        operations: [operation]
+      };
+
+      const result = await diffEngine.applyDiff(workflowWithAI as Workflow, request);
+
+      expect(result.success).toBe(true);
+      expect(result.workflow.connections['Calculator']).toBeDefined();
+      expect(result.workflow.connections['Calculator']['ai_tool']).toBeDefined();
+      // The inner type should be 'ai_tool', NOT 'main'
+      expect(result.workflow.connections['Calculator']['ai_tool'][0][0].type).toBe('ai_tool');
+      expect(result.workflow.connections['Calculator']['ai_tool'][0][0].node).toBe('AI Agent');
+    });
+
+    it('should propagate ai_languageModel connection type', async () => {
+      const workflowWithAI = {
+        ...baseWorkflow,
+        nodes: [
+          {
+            id: 'agent1',
+            name: 'AI Agent',
+            type: '@n8n/n8n-nodes-langchain.agent',
+            typeVersion: 2.1,
+            position: [500, 300] as [number, number],
+            parameters: {}
+          },
+          {
+            id: 'llm1',
+            name: 'OpenAI Chat Model',
+            type: '@n8n/n8n-nodes-langchain.lmChatOpenAi',
+            typeVersion: 1.2,
+            position: [300, 200] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const operation: AddConnectionOperation = {
+        type: 'addConnection',
+        source: 'OpenAI Chat Model',
+        target: 'AI Agent',
+        sourceOutput: 'ai_languageModel'
+      };
+
+      const request: WorkflowDiffRequest = {
+        id: 'test-workflow',
+        operations: [operation]
+      };
+
+      const result = await diffEngine.applyDiff(workflowWithAI as Workflow, request);
+
+      expect(result.success).toBe(true);
+      expect(result.workflow.connections['OpenAI Chat Model']['ai_languageModel'][0][0].type).toBe('ai_languageModel');
+    });
+
+    it('should propagate ai_memory connection type', async () => {
+      const workflowWithAI = {
+        ...baseWorkflow,
+        nodes: [
+          {
+            id: 'agent1',
+            name: 'AI Agent',
+            type: '@n8n/n8n-nodes-langchain.agent',
+            typeVersion: 2.1,
+            position: [500, 300] as [number, number],
+            parameters: {}
+          },
+          {
+            id: 'memory1',
+            name: 'Window Buffer Memory',
+            type: '@n8n/n8n-nodes-langchain.memoryBufferWindow',
+            typeVersion: 1.3,
+            position: [300, 500] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const operation: AddConnectionOperation = {
+        type: 'addConnection',
+        source: 'Window Buffer Memory',
+        target: 'AI Agent',
+        sourceOutput: 'ai_memory'
+      };
+
+      const request: WorkflowDiffRequest = {
+        id: 'test-workflow',
+        operations: [operation]
+      };
+
+      const result = await diffEngine.applyDiff(workflowWithAI as Workflow, request);
+
+      expect(result.success).toBe(true);
+      expect(result.workflow.connections['Window Buffer Memory']['ai_memory'][0][0].type).toBe('ai_memory');
+    });
+
+    it('should allow explicit targetInput override for mixed connection types', async () => {
+      const workflowWithNodes = {
+        ...baseWorkflow,
+        nodes: [
+          {
+            id: 'node1',
+            name: 'Source Node',
+            type: 'n8n-nodes-base.set',
+            typeVersion: 3.4,
+            position: [300, 300] as [number, number],
+            parameters: {}
+          },
+          {
+            id: 'node2',
+            name: 'Target Node',
+            type: 'n8n-nodes-base.set',
+            typeVersion: 3.4,
+            position: [500, 300] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const operation: AddConnectionOperation = {
+        type: 'addConnection',
+        source: 'Source Node',
+        target: 'Target Node',
+        sourceOutput: 'main',
+        targetInput: 'main' // Explicit override
+      };
+
+      const request: WorkflowDiffRequest = {
+        id: 'test-workflow',
+        operations: [operation]
+      };
+
+      const result = await diffEngine.applyDiff(workflowWithNodes as Workflow, request);
+
+      expect(result.success).toBe(true);
+      expect(result.workflow.connections['Source Node']['main'][0][0].type).toBe('main');
+    });
+
+    it('should default to main for regular connections when sourceOutput is not specified', async () => {
+      const workflowWithNodes = {
+        ...baseWorkflow,
+        nodes: [
+          {
+            id: 'node1',
+            name: 'Source Node',
+            type: 'n8n-nodes-base.set',
+            typeVersion: 3.4,
+            position: [300, 300] as [number, number],
+            parameters: {}
+          },
+          {
+            id: 'node2',
+            name: 'Target Node',
+            type: 'n8n-nodes-base.set',
+            typeVersion: 3.4,
+            position: [500, 300] as [number, number],
+            parameters: {}
+          }
+        ],
+        connections: {}
+      };
+
+      const operation: AddConnectionOperation = {
+        type: 'addConnection',
+        source: 'Source Node',
+        target: 'Target Node'
+        // Neither sourceOutput nor targetInput specified - should default to 'main'
+      };
+
+      const request: WorkflowDiffRequest = {
+        id: 'test-workflow',
+        operations: [operation]
+      };
+
+      const result = await diffEngine.applyDiff(workflowWithNodes as Workflow, request);
+
+      expect(result.success).toBe(true);
+      expect(result.workflow.connections['Source Node']['main'][0][0].type).toBe('main');
+    });
+  });
 });