n8n_update_partial_workflow: operations array received as string from Claude Code (VS Code extension)

[YerayRodri]

Bug Description

When calling n8n_update_partial_workflow from Claude Code (VS Code extension), the operations parameter arrives at the MCP server as a string instead of an array, causing Zod validation to fail.

Error Received

{
  "success": false,
  "error": "Invalid input",
  "details": {
    "errors": [
      {
        "code": "invalid_type",
        "expected": "array",
        "received": "string",
        "path": ["operations"],
        "message": "Expected array, received string"
      }
    ]
  }
}

Environment

• MCP Server version: 2.35.2 (Docker image 2026-02-10)
• Docker image: ghcr.io/czlonkowski/n8n-mcp:latest
• Client: Claude Code (VS Code extension)
• MCP Mode: stdio
• Platform: macOS Darwin 25.2.0

Steps to Reproduce

Call n8n_update_partial_workflow with any operation array from Claude Code:

{
  "id": "wf_id",
  "intent": "Rename workflow",
  "operations": [{"type": "updateName", "name": "New Name"}]
}

Expected Behavior

The operations parameter is parsed as an array and the operation is applied successfully.

Actual Behavior

The MCP server receives operations as a JSON string instead of a native array and Zod rejects it with invalid_type.

Possible Fix

Add a Zod preprocessor to coerce JSON strings to arrays before validation:

operations: z.preprocess(
  (val) => (typeof val === "string" ? JSON.parse(val) : val),
  z.array(operationSchema)
)

Notes

All other tools with simple string parameters work correctly (n8n_list_workflows, n8n_get_workflow, n8n_autofix_workflow, n8n_health_check). Only tools requiring array parameters are affected.