How can I fix the 'Received tool input did not match expected schema' error in my n8n workflow?

Below is a checklist of steps you can follow to troubleshoot and address the error:

1. Check the Output Format

Ensure that the AI Agent’s output is structured exactly as the Google Sheets tool expects. If the returned JSON deviates from the schema, the Google Sheets node will throw the error. To do so, you can:

• Enable the “Require Specific Output Format” option in the Tools Agent node and provide a JSON schema that matches the Google Sheets node requirements.
• Verify that your prompt and any formatting instructions lead the AI to output valid JSON that exactly adheres to that schema.

2. Inspect Intermediate Output

Before passing the data to the Google Sheets node, inspect the output using a node like “Set” or “Function” to log the returned value. This can help pinpoint if certain runs return unexpected or null values.

3. Validate Dynamic Expressions

If you’re using expressions to build the prompt or populate parameters, make sure they correctly resolve to valid and non-null values on every run. A mismatch or null value in one of these cases can lead to schema issues.

4. Review Version and Compatibility

Since you’re self-hosting the latest version of n8n, confirm that all nodes (especially the Google Sheets tool node) are running on the expected versions. If you imported a workflow template, try removing and re-adding the Google Sheets node to ensure it’s using the latest schema definitions.

Example: Enforcing a JSON Schema Format

You can add a “Require Specific Output Format” configuration similar to this (adjust based on your exact schema requirements):

JSONCopied
{
  "type": "object",
  "properties": {
    "data": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "columnA": { "type": "string" },
          "columnB": { "type": "number" }
        },
        "required": ["columnA", "columnB"]
      }
    }
  },
  "required": ["data"]
}

This forces the AI to output JSON that includes a “data” array with items matching the schema expected by the Google Sheets node.

Summary

• Format: Ensure the Tools Agent returns data in the exact JSON format/structure expected by the Google Sheets node.
• Debug: Inspect the output at intermediate steps to catch deviations.
• Expressions: Review and validate any dynamic input expressions that may inadvertently return null or incorrect values.

Taking these steps should help resolve the “Received tool input did not match expected schema” error in your workflow.