feat: Add workflow activation/deactivation via diff operations

Implements workflow activation and deactivation as diff operations in
n8n_update_partial_workflow tool, following the pattern of other
configuration operations.

Changes:
- Add activateWorkflow/deactivateWorkflow API methods
- Add operation types to diff engine
- Update tool documentation
- Remove activation limitation

Resolves #399
Credits: ArtemisAI, cmj-hub for investigation and initial implementation
Conceived by Romuald Członkowski - www.aiadvisors.pl/en

CHANGELOG.md

@@ -7,6 +7,111 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.22.11] - 2025-01-06
+
+### ✨ New Features
+
+**Issue #399: Workflow Activation via Diff Operations**
+
+Added workflow activation and deactivation as diff operations in `n8n_update_partial_workflow`, using n8n's dedicated API endpoints.
+
+#### Problem
+
+The n8n API provides dedicated `POST /workflows/{id}/activate` and `POST /workflows/{id}/deactivate` endpoints, but these were not accessible through n8n-mcp. Users could not programmatically control workflow activation status, forcing manual activation through the n8n UI.
+
+#### Solution
+
+Implemented activation/deactivation as diff operations, following the established pattern of metadata operations like `updateSettings` and `updateName`. This keeps the tool count manageable (40 tools, not 42) and provides a consistent interface.
+
+#### Changes
+
+**API Client** (`src/services/n8n-api-client.ts`):
+- Added `activateWorkflow(id: string): Promise<Workflow>` method
+- Added `deactivateWorkflow(id: string): Promise<Workflow>` method
+- Both use POST requests to dedicated n8n API endpoints
+
+**Diff Engine Types** (`src/types/workflow-diff.ts`):
+- Added `ActivateWorkflowOperation` interface
+- Added `DeactivateWorkflowOperation` interface
+- Added `shouldActivate` and `shouldDeactivate` flags to `WorkflowDiffResult`
+- Increased supported operations from 15 to 17
+
+**Diff Engine** (`src/services/workflow-diff-engine.ts`):
+- Added validation for activation (requires activatable triggers)
+- Added operation application logic
+- Transfers activation intent from workflow object to result
+- Validates workflow has activatable triggers (webhook, schedule, etc.)
+- Rejects workflows with only `executeWorkflowTrigger` (cannot activate)
+
+**Handler** (`src/mcp/handlers-workflow-diff.ts`):
+- Checks `shouldActivate` and `shouldDeactivate` flags after workflow update
+- Calls appropriate API methods
+- Includes activation status in response message and details
+- Handles activation/deactivation errors gracefully
+
+**Documentation** (`src/mcp/tool-docs/workflow_management/n8n-update-partial-workflow.ts`):
+- Updated operation count from 15 to 17
+- Added "Workflow Activation Operations" section
+- Added activation tip to essentials
+
+**Tool Registration** (`src/mcp/handlers-n8n-manager.ts`):
+- Removed "Cannot activate/deactivate workflows via API" from limitations
+
+#### Usage
+
+```javascript
+// Activate workflow
+n8n_update_partial_workflow({
+  id: "workflow_id",
+  operations: [{
+    type: "activateWorkflow"
+  }]
+})
+
+// Deactivate workflow
+n8n_update_partial_workflow({
+  id: "workflow_id",
+  operations: [{
+    type: "deactivateWorkflow"
+  }]
+})
+
+// Combine with other operations
+n8n_update_partial_workflow({
+  id: "workflow_id",
+  operations: [
+    {type: "updateNode", nodeId: "abc", updates: {name: "Updated"}},
+    {type: "activateWorkflow"}
+  ]
+})
+```
+
+#### Validation
+
+- **Activation**: Requires at least one enabled activatable trigger node
+- **Deactivation**: Always valid
+- **Error Handling**: Clear messages when activation fails due to missing triggers
+- **Trigger Detection**: Uses `isActivatableTrigger()` utility (Issue #351 compliance)
+
+#### Benefits
+
+- ✅ Consistent with existing architecture (metadata operations pattern)
+- ✅ Keeps tool count at 40 (not 42)
+- ✅ Atomic operations - activation happens after workflow update
+- ✅ Proper validation - prevents activation without triggers
+- ✅ Clear error messages - guides users on trigger requirements
+- ✅ Works with other operations - can update and activate in one call
+
+#### Credits
+
+- **@ArtemisAI** - Original investigation and API endpoint discovery
+- **@cmj-hub** - Implementation attempt and PR contribution
+- Architectural guidance from project maintainer
+
+Resolves #399
+
+Conceived by Romuald Członkowski - [www.aiadvisors.pl/en](https://www.aiadvisors.pl/en)
+
 ## [2.22.10] - 2025-11-04
 
 ### 🐛 Bug Fixes

package.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp",
-  "version": "2.22.10",
+  "version": "2.22.11",
   "description": "Integration between n8n workflow automation and Model Context Protocol (MCP)",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",

package.runtime.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp-runtime",
-  "version": "2.22.10",
+  "version": "2.22.11",
   "description": "n8n MCP Server Runtime Dependencies Only",
   "private": true,
   "dependencies": {

src/mcp/handlers-n8n-manager.ts

@@ -1561,7 +1561,6 @@ export async function handleListAvailableTools(context?: InstanceContext): Promi
         maxRetries: config.maxRetries
       } : null,
       limitations: [
-        'Cannot activate/deactivate workflows via API',
         'Cannot execute workflows directly (must use webhooks)',
         'Cannot stop running executions',
         'Tags and credentials have limited API support'

src/mcp/handlers-workflow-diff.ts

@@ -245,15 +245,52 @@ export async function handleUpdatePartialWorkflow(
     // Update workflow via API
     try {
       const updatedWorkflow = await client.updateWorkflow(input.id, diffResult.workflow!);
-      
+
+      // Handle activation/deactivation if requested
+      let finalWorkflow = updatedWorkflow;
+      let activationMessage = '';
+
+      if (diffResult.shouldActivate) {
+        try {
+          finalWorkflow = await client.activateWorkflow(input.id);
+          activationMessage = ' Workflow activated.';
+        } catch (activationError) {
+          logger.error('Failed to activate workflow after update', activationError);
+          return {
+            success: false,
+            error: 'Workflow updated successfully but activation failed',
+            details: {
+              workflowUpdated: true,
+              activationError: activationError instanceof Error ? activationError.message : 'Unknown error'
+            }
+          };
+        }
+      } else if (diffResult.shouldDeactivate) {
+        try {
+          finalWorkflow = await client.deactivateWorkflow(input.id);
+          activationMessage = ' Workflow deactivated.';
+        } catch (deactivationError) {
+          logger.error('Failed to deactivate workflow after update', deactivationError);
+          return {
+            success: false,
+            error: 'Workflow updated successfully but deactivation failed',
+            details: {
+              workflowUpdated: true,
+              deactivationError: deactivationError instanceof Error ? deactivationError.message : 'Unknown error'
+            }
+          };
+        }
+      }
+
       return {
         success: true,
-        data: updatedWorkflow,
+        data: finalWorkflow,
-        message: `Workflow "${updatedWorkflow.name}" updated successfully. Applied ${diffResult.operationsApplied} operations.`,
+        message: `Workflow "${finalWorkflow.name}" updated successfully. Applied ${diffResult.operationsApplied} operations.${activationMessage}`,
         details: {
           operationsApplied: diffResult.operationsApplied,
-          workflowId: updatedWorkflow.id,
+          workflowId: finalWorkflow.id,
-          workflowName: updatedWorkflow.name,
+          workflowName: finalWorkflow.name,
+          active: finalWorkflow.active,
           applied: diffResult.applied,
           failed: diffResult.failed,
           errors: diffResult.errors,

src/mcp/tool-docs/workflow_management/n8n-update-partial-workflow.ts

@@ -4,7 +4,7 @@ export const n8nUpdatePartialWorkflowDoc: ToolDocumentation = {
   name: 'n8n_update_partial_workflow',
   category: 'workflow_management',
   essentials: {
-    description: 'Update workflow incrementally with diff operations. Types: addNode, removeNode, updateNode, moveNode, enable/disableNode, addConnection, removeConnection, rewireConnection, cleanStaleConnections, replaceConnections, updateSettings, updateName, add/removeTag. Supports smart parameters (branch, case) for multi-output nodes. Full support for AI connections (ai_languageModel, ai_tool, ai_memory, ai_embedding, ai_vectorStore, ai_document, ai_textSplitter, ai_outputParser).',
+    description: 'Update workflow incrementally with diff operations. Types: addNode, removeNode, updateNode, moveNode, enable/disableNode, addConnection, removeConnection, rewireConnection, cleanStaleConnections, replaceConnections, updateSettings, updateName, add/removeTag, activateWorkflow, deactivateWorkflow. Supports smart parameters (branch, case) for multi-output nodes. Full support for AI connections (ai_languageModel, ai_tool, ai_memory, ai_embedding, ai_vectorStore, ai_document, ai_textSplitter, ai_outputParser).',
     keyParameters: ['id', 'operations', 'continueOnError'],
     example: 'n8n_update_partial_workflow({id: "wf_123", operations: [{type: "rewireConnection", source: "IF", from: "Old", to: "New", branch: "true"}]})',
     performance: 'Fast (50-200ms)',
@@ -19,11 +19,12 @@ export const n8nUpdatePartialWorkflowDoc: ToolDocumentation = {
       'For AI connections, specify sourceOutput type (ai_languageModel, ai_tool, etc.)',
       'Batch AI component connections for atomic updates',
       'Auto-sanitization: ALL nodes auto-fixed during updates (operator structures, missing metadata)',
-      'Node renames automatically update all connection references - no manual connection operations needed'
+      'Node renames automatically update all connection references - no manual connection operations needed',
+      'Activate/deactivate workflows: Use activateWorkflow/deactivateWorkflow operations (requires activatable triggers like webhook/schedule)'
     ]
   },
   full: {
-    description: `Updates workflows using surgical diff operations instead of full replacement. Supports 15 operation types for precise modifications. Operations are validated and applied atomically by default - all succeed or none are applied.
+    description: `Updates workflows using surgical diff operations instead of full replacement. Supports 17 operation types for precise modifications. Operations are validated and applied atomically by default - all succeed or none are applied.
 
 ## Available Operations:
 
@@ -48,6 +49,10 @@ export const n8nUpdatePartialWorkflowDoc: ToolDocumentation = {
 - **addTag**: Add a workflow tag
 - **removeTag**: Remove a workflow tag
 
+### Workflow Activation Operations (2 types):
+- **activateWorkflow**: Activate the workflow to enable automatic execution via triggers
+- **deactivateWorkflow**: Deactivate the workflow to prevent automatic execution
+
 ## Smart Parameters for Multi-Output Nodes
 
 For **IF nodes**, use semantic 'branch' parameter instead of technical sourceIndex:

src/services/n8n-api-client.ts

@@ -170,6 +170,24 @@ export class N8nApiClient {
     }
   }
 
+  async activateWorkflow(id: string): Promise<Workflow> {
+    try {
+      const response = await this.client.post(`/workflows/${id}/activate`);
+      return response.data;
+    } catch (error) {
+      throw handleN8nApiError(error);
+    }
+  }
+
+  async deactivateWorkflow(id: string): Promise<Workflow> {
+    try {
+      const response = await this.client.post(`/workflows/${id}/deactivate`);
+      return response.data;
+    } catch (error) {
+      throw handleN8nApiError(error);
+    }
+  }
+
   /**
    * Lists workflows from n8n instance.
    *

src/services/workflow-diff-engine.ts

@@ -25,6 +25,8 @@ import {
   UpdateNameOperation,
   AddTagOperation,
   RemoveTagOperation,
+  ActivateWorkflowOperation,
+  DeactivateWorkflowOperation,
   CleanStaleConnectionsOperation,
   ReplaceConnectionsOperation
 } from '../types/workflow-diff';
@@ -32,6 +34,7 @@ import { Workflow, WorkflowNode, WorkflowConnection } from '../types/n8n-api';
 import { Logger } from '../utils/logger';
 import { validateWorkflowNode, validateWorkflowConnections } from './n8n-validation';
 import { sanitizeNode, sanitizeWorkflowNodes } from './node-sanitizer';
+import { isActivatableTrigger } from '../utils/node-type-utils';
 
 const logger = new Logger({ prefix: '[WorkflowDiffEngine]' });
 
@@ -214,12 +217,23 @@ export class WorkflowDiffEngine {
         }
 
         const operationsApplied = request.operations.length;
+
+        // Extract activation flags from workflow object
+        const shouldActivate = (workflowCopy as any)._shouldActivate === true;
+        const shouldDeactivate = (workflowCopy as any)._shouldDeactivate === true;
+
+        // Clean up temporary flags
+        delete (workflowCopy as any)._shouldActivate;
+        delete (workflowCopy as any)._shouldDeactivate;
+
         return {
           success: true,
           workflow: workflowCopy,
           operationsApplied,
           message: `Successfully applied ${operationsApplied} operations (${nodeOperations.length} node ops, ${otherOperations.length} other ops)`,
-          warnings: this.warnings.length > 0 ? this.warnings : undefined
+          warnings: this.warnings.length > 0 ? this.warnings : undefined,
+          shouldActivate: shouldActivate || undefined,
+          shouldDeactivate: shouldDeactivate || undefined
         };
       }
     } catch (error) {
@@ -262,6 +276,10 @@ export class WorkflowDiffEngine {
       case 'addTag':
       case 'removeTag':
         return null; // These are always valid
+      case 'activateWorkflow':
+        return this.validateActivateWorkflow(workflow, operation);
+      case 'deactivateWorkflow':
+        return this.validateDeactivateWorkflow(workflow, operation);
       case 'cleanStaleConnections':
         return this.validateCleanStaleConnections(workflow, operation);
       case 'replaceConnections':
@@ -315,6 +333,12 @@ export class WorkflowDiffEngine {
       case 'removeTag':
         this.applyRemoveTag(workflow, operation);
         break;
+      case 'activateWorkflow':
+        this.applyActivateWorkflow(workflow, operation);
+        break;
+      case 'deactivateWorkflow':
+        this.applyDeactivateWorkflow(workflow, operation);
+        break;
       case 'cleanStaleConnections':
         this.applyCleanStaleConnections(workflow, operation);
         break;
@@ -847,13 +871,46 @@ export class WorkflowDiffEngine {
 
   private applyRemoveTag(workflow: Workflow, operation: RemoveTagOperation): void {
     if (!workflow.tags) return;
-    
+
     const index = workflow.tags.indexOf(operation.tag);
     if (index !== -1) {
       workflow.tags.splice(index, 1);
     }
   }
 
+  // Workflow activation operation validators
+  private validateActivateWorkflow(workflow: Workflow, operation: ActivateWorkflowOperation): string | null {
+    // Check if workflow has at least one activatable trigger
+    // Issue #351: executeWorkflowTrigger cannot activate workflows
+    const activatableTriggers = workflow.nodes.filter(
+      node => !node.disabled && isActivatableTrigger(node.type)
+    );
+
+    if (activatableTriggers.length === 0) {
+      return 'Cannot activate workflow: No activatable trigger nodes found. Workflows must have at least one enabled trigger node (webhook, schedule, email, etc.). Note: executeWorkflowTrigger cannot activate workflows as they can only be invoked by other workflows.';
+    }
+
+    return null;
+  }
+
+  private validateDeactivateWorkflow(workflow: Workflow, operation: DeactivateWorkflowOperation): string | null {
+    // Deactivation is always valid - any workflow can be deactivated
+    return null;
+  }
+
+  // Workflow activation operation appliers
+  private applyActivateWorkflow(workflow: Workflow, operation: ActivateWorkflowOperation): void {
+    // Set flag in workflow object to indicate activation intent
+    // The handler will call the API method after workflow update
+    (workflow as any)._shouldActivate = true;
+  }
+
+  private applyDeactivateWorkflow(workflow: Workflow, operation: DeactivateWorkflowOperation): void {
+    // Set flag in workflow object to indicate deactivation intent
+    // The handler will call the API method after workflow update
+    (workflow as any)._shouldDeactivate = true;
+  }
+
   // Connection cleanup operation validators
   private validateCleanStaleConnections(workflow: Workflow, operation: CleanStaleConnectionsOperation): string | null {
     // This operation is always valid - it just cleans up what it finds

src/types/workflow-diff.ts

@@ -114,6 +114,16 @@ export interface RemoveTagOperation extends DiffOperation {
   tag: string;
 }
 
+export interface ActivateWorkflowOperation extends DiffOperation {
+  type: 'activateWorkflow';
+  // No additional properties needed - just activates the workflow
+}
+
+export interface DeactivateWorkflowOperation extends DiffOperation {
+  type: 'deactivateWorkflow';
+  // No additional properties needed - just deactivates the workflow
+}
+
 // Connection Cleanup Operations
 export interface CleanStaleConnectionsOperation extends DiffOperation {
   type: 'cleanStaleConnections';
@@ -148,6 +158,8 @@ export type WorkflowDiffOperation =
   | UpdateNameOperation
   | AddTagOperation
   | RemoveTagOperation
+  | ActivateWorkflowOperation
+  | DeactivateWorkflowOperation
   | CleanStaleConnectionsOperation
   | ReplaceConnectionsOperation;
 
@@ -176,6 +188,8 @@ export interface WorkflowDiffResult {
   applied?: number[]; // Indices of successfully applied operations (when continueOnError is true)
   failed?: number[]; // Indices of failed operations (when continueOnError is true)
   staleConnectionsRemoved?: Array<{ from: string; to: string }>; // For cleanStaleConnections operation
+  shouldActivate?: boolean; // Flag to activate workflow after update (for activateWorkflow operation)
+  shouldDeactivate?: boolean; // Flag to deactivate workflow after update (for deactivateWorkflow operation)
 }
 
 // Helper type for node reference (supports both ID and name)