# Story 2.4: Implement PATCH /workflows/{id}
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## Status
**✅ COMPLETED** - December 26, 2024
**Solution:** Returns informative guidance message instead of API error
**Implementation Status:**
- ✅ Code implementation complete
- ✅ MCP tool registered and enabled
- ✅ Returns helpful guidance when called
- ✅ Provides workaround steps
- ✅ No errors - graceful handling
**API Limitation:** n8n API does not support PATCH method (tested v1.82.3, v2.1.4)
**User Experience:** Tool provides clear guidance and alternative solutions
**Details:** See `docs/STORY-2.4-API-LIMITATION-DISCOVERY.md`
## Story
**As a** workflow automation user,
**I want** to partially update workflow properties without replacing the entire workflow structure,
**so that** I can make targeted changes (like updating name, tags, or settings) without needing to retrieve and send back the complete workflow with all nodes and connections.
## Acceptance Criteria
1. New `patch_workflow` MCP tool registered and functional
2. Tool supports partial workflow updates per PATCH /workflows/{id} API specification
3. Only provided fields are updated, others remain unchanged
4. Multi-instance routing works correctly for PATCH operation
5. Request/response formats match n8n API documentation
6. Error handling for non-existent workflows (404)
7. Error handling for invalid partial update data (400)
8. Comprehensive testing with various partial update scenarios
9. Documentation updated with PATCH method usage
10. Integration with existing test infrastructure
## Tasks / Subtasks
### Task 1: Analyze PATCH Endpoint Documentation (AC: 2, 5)
- [ ] Read complete PATCH /workflows/{id} specification from docs/n8n-api-docs/10-WORKFLOWS-API.md
- [ ] Identify all fields that can be partially updated
- [ ] Document PATCH vs PUT behavioral differences
- [ ] Note any documented limitations or constraints
- [ ] Create implementation specification
### Task 2: Implement patch_workflow Method in N8NApiWrapper (AC: 1, 2, 3, 4)
- [ ] Add `patchWorkflow` method to `src/services/n8nApiWrapper.ts`
- [ ] Implement using `callWithInstance` pattern for multi-instance support
- [ ] Use axios PATCH method instead of PUT
- [ ] Support partial update payload structure
- [ ] Add appropriate error handling
- [ ] Add debug logging for transparency
- [ ] Code follows existing method patterns in wrapper
### Task 3: Register patch_workflow MCP Tool (AC: 1, 4, 5)
- [ ] Add `patch_workflow` tool definition to `src/index.ts`
- [ ] Define input schema with partial update fields
- [ ] Include instance parameter for multi-instance routing
- [ ] Add comprehensive tool description
- [ ] Document which fields can be partially updated
- [ ] Implement tool request handler
- [ ] Map to `N8NApiWrapper.patchWorkflow` method
### Task 4: Implement Partial Update Logic (AC: 2, 3)
- [ ] Support partial update of workflow name
- [ ] Support partial update of tags array
- [ ] Support partial update of settings object
- [ ] Support partial update of active status
- [ ] Ensure unspecified fields are not modified
- [ ] Handle null values appropriately (remove field vs ignore)
- [ ] Validate partial update payload structure
### Task 5: Error Handling Implementation (AC: 6, 7)
- [ ] Handle 404 Not Found for non-existent workflow IDs
- [ ] Handle 400 Bad Request for invalid partial update data
- [ ] Handle 401 Unauthorized for invalid API keys
- [ ] Provide descriptive error messages
- [ ] Test error scenarios with multi-instance context
- [ ] Ensure error format consistent with other methods
### Task 6: Create Comprehensive Tests (AC: 8)
- [ ] **Test 6.1**: Partial update of workflow name only
- [ ] Create workflow with initial name
- [ ] PATCH with new name only
- [ ] Verify name updated, all other fields unchanged
- [ ] **Test 6.2**: Partial update of tags only
- [ ] Create workflow with initial tags
- [ ] PATCH with new tags array
- [ ] Verify tags updated, other fields unchanged
- [ ] **Test 6.3**: Partial update of settings only
- [ ] Create workflow with initial settings
- [ ] PATCH with modified settings
- [ ] Verify settings updated, other fields unchanged
- [ ] **Test 6.4**: Partial update of active status only
- [ ] Create inactive workflow
- [ ] PATCH with active: true
- [ ] Verify active status changed, other fields unchanged
- [ ] **Test 6.5**: Multiple field partial update
- [ ] PATCH with name + tags + settings
- [ ] Verify all specified fields updated
- [ ] Verify unspecified fields unchanged (nodes, connections)
- [ ] **Test 6.6**: PATCH vs PUT comparison
- [ ] Create workflow with complex structure
- [ ] PATCH with partial update
- [ ] Verify nodes/connections preserved (vs PUT which replaces all)
- [ ] **Test 6.7**: Multi-instance PATCH
- [ ] PATCH workflow in default instance
- [ ] PATCH workflow in specific instance
- [ ] Verify instance routing works
- [ ] **Test 6.8**: Error scenarios
- [ ] PATCH non-existent workflow (expect 404)
- [ ] PATCH with invalid field values (expect 400)
- [ ] PATCH with malformed JSON
- [ ] Verify error responses
- [ ] **Test 6.9**: Edge cases
- [ ] PATCH with empty update object
- [ ] PATCH with null values
- [ ] PATCH with undefined fields
### Task 7: Update Documentation (AC: 9)
- [ ] Update README.md with PATCH method example
- [ ] Update CLAUDE.md with PATCH implementation notes
- [ ] Add PATCH method to MCP tools list in README
- [ ] Document PATCH vs PUT differences clearly
- [ ] Add code examples for common PATCH use cases
- [ ] Update CHANGELOG.md with version bump
- [ ] Document any discovered limitations
### Task 8: Integration with Test Infrastructure (AC: 10)
- [ ] Add patch_workflow tests to `test-mcp-tools.js`
- [ ] Ensure tests run independently
- [ ] Add cleanup after tests
- [ ] Document test execution procedure
- [ ] Verify no regression in existing tests
## Dev Notes
### Relevant Source Tree
**Files to Create/Modify:**
- `src/services/n8nApiWrapper.ts` - Add `patchWorkflow` method
- `src/index.ts` - Add `patch_workflow` MCP tool registration
- `test-mcp-tools.js` - Add PATCH tests
- `README.md` - Add PATCH documentation
- `CLAUDE.md` - Add PATCH implementation notes
- `CHANGELOG.md` - Version bump and change notes
**Reference Files:**
- `docs/n8n-api-docs/10-WORKFLOWS-API.md` - Lines ~501-550: PATCH documentation
- Existing `update_workflow` implementation (PUT) - Pattern reference
### Current Implementation Context
**Existing PUT Method (update_workflow):**
Located in `src/index.ts`:389 and `N8NApiWrapper`
```typescript
// PUT - Full replacement
const response = await api.put(`/workflows/${id}`, workflowData);
```
**New PATCH Method Pattern:**
```typescript
// PATCH - Partial update
public async patchWorkflow(
instanceSlug: string | undefined,
workflowId: string,
partialUpdate: Partial<WorkflowUpdatePayload>
): Promise<Workflow> {
return this.callWithInstance(instanceSlug, async () => {
const api = this.envManager.getApiInstance(instanceSlug);
const response = await api.patch(`/workflows/${workflowId}`, partialUpdate);
return response.data;
});
}
```
### PATCH vs PUT Differences
**PUT (Existing update_workflow):**
- Replaces entire workflow object
- Requires sending complete workflow structure
- All fields must be provided (name, nodes, connections, settings, etc.)
- Missing fields will be removed/reset
**PATCH (New patch_workflow):**
- Updates only specified fields
- Partial payload allowed
- Unspecified fields remain unchanged
- Ideal for targeted updates (name, tags, settings)
**Use Cases:**
- **PATCH**: Change workflow name, update tags, modify settings, toggle active status
- **PUT**: Restructure workflow, modify nodes/connections, complete workflow replacement
### MCP Tool Input Schema
```typescript
{
name: 'patch_workflow',
description: 'Partially update an existing workflow (only specified fields will be changed)',
inputSchema: {
type: 'object',
properties: {
workflowId: {
type: 'string',
description: 'ID of the workflow to partially update'
},
partialUpdate: {
type: 'object',
description: 'Object containing only the fields to update',
properties: {
name: {
type: 'string',
description: 'New workflow name (optional)'
},
tags: {
type: 'array',
items: { type: 'string' },
description: 'New tags array (optional)'
},
settings: {
type: 'object',
description: 'New settings object (optional)'
},
active: {
type: 'boolean',
description: 'New active status (optional)'
}
}
},
instance: {
type: 'string',
description: 'Instance identifier (optional)'
}
},
required: ['workflowId', 'partialUpdate']
}
}
```
### Implementation Pattern
Follow existing method patterns from `N8NApiWrapper`:
1. **Method Signature:**
```typescript
public async patchWorkflow(
instanceSlug: string | undefined,
workflowId: string,
partialUpdate: Partial<WorkflowUpdatePayload>
): Promise<Workflow>
```
2. **Implementation:**
```typescript
return this.callWithInstance(instanceSlug, async () => {
const api = this.envManager.getApiInstance(instanceSlug);
const response = await api.patch(`/workflows/${workflowId}`, partialUpdate);
return response.data;
});
```
3. **Error Handling:**
- Wrapped by `callWithInstance` - automatic error handling
- Additional context in error messages
- Logged to stderr via console.error()
### Key Implementation Points
1. **Axios PATCH Method:**
- Use `api.patch()` instead of `api.put()`
- URL: `/workflows/${workflowId}`
- Payload: Partial update object
2. **Multi-Instance Support:**
- Use `callWithInstance` pattern
- Pass instance parameter through all layers
- Instance routing handled by EnvironmentManager
3. **Validation:**
- Validate workflowId is provided
- Validate partialUpdate is an object
- Let n8n API handle field-level validation
4. **Response:**
- Return complete updated workflow object
- Same structure as GET /workflows/{id}
### Testing Strategy
**Test File:** `test-patch-workflow.js` or integrate into `test-mcp-tools.js`
**Test Scenarios:**
1. Partial update single field (name, tags, settings, active)
2. Partial update multiple fields
3. Verify unspecified fields unchanged
4. Compare PATCH vs PUT behavior
5. Multi-instance routing
6. Error scenarios (404, 400, 401)
7. Edge cases (empty update, null values)
**Test Pattern:**
```javascript
async function testPatchWorkflow() {
// 1. Create test workflow
const workflow = await createWorkflow({
name: 'Original Name',
tags: ['tag1'],
nodes: [...],
connections: {...}
});
// 2. PATCH with partial update
const updated = await patchWorkflow(workflow.id, {
name: 'Updated Name'
});
// 3. Verify
assert(updated.name === 'Updated Name');
assert(updated.tags[0] === 'tag1'); // Unchanged
assert(updated.nodes.length === workflow.nodes.length); // Unchanged
}
```
### Documentation References
**API Documentation:**
- `docs/n8n-api-docs/10-WORKFLOWS-API.md` - Lines ~501-550
- PATCH /api/v1/workflows/{id} specification
**Implementation References:**
- Existing PUT method: `src/index.ts:389`
- N8NApiWrapper pattern: `src/services/n8nApiWrapper.ts`
- Multi-instance pattern: All existing methods
**Testing References:**
- Existing workflow tests: `test-mcp-tools.js`
- Workflow CRUD patterns
## Testing
### Test Approach
**Phase 1: Basic PATCH Functionality**
- Implement method
- Test single field updates
- Verify partial update behavior
**Phase 2: Multi-Field Updates**
- Test multiple field updates
- Verify field isolation (unspecified fields unchanged)
**Phase 3: PATCH vs PUT Comparison**
- Create identical workflows
- Update using PATCH and PUT
- Compare results and behavior
**Phase 4: Multi-Instance Testing**
- Test PATCH across instances
- Verify instance routing
**Phase 5: Error Scenarios**
- Test all error conditions
- Verify error responses
**Phase 6: Documentation & Integration**
- Update all documentation
- Integrate into test suite
### Edge Cases to Test
1. **Empty Update**: `partialUpdate: {}`
2. **Null Values**: Fields set to null
3. **Nested Objects**: Partial update of settings sub-objects
4. **Array Replacement**: Tags array vs individual tag modification
5. **Active Status**: Toggle between true/false multiple times
6. **Large Workflow**: PATCH on workflow with 50+ nodes
7. **Concurrent PATCH**: Simultaneous PATCH requests to same workflow
## Change Log
| Date | Version | Description | Author |
|------|---------|-------------|--------|
| 2025-12-26 | 1.0 | Story created for PATCH /workflows/{id} implementation | Sarah (PO) |
## Dev Agent Record
*This section will be populated by the development agent during implementation.*
### Agent Model Used
*To be filled by dev agent*
### Debug Log References
*To be filled by dev agent*
### Completion Notes List
*To be filled by dev agent*
### File List
*To be filled by dev agent*
## QA Results
*This section will be populated by QA agent after implementation and validation.*
