Why does the serp_retriever subworkflow intermittently fail to return a response in my AI agent?

Below is an explanation of the issue based on your description:

What’s Happening

Your main AI agent relies on two sub-workflow tools. Even though both sub-workflows run successfully according to their logs, the main agent sometimes reports this error:

“The workflow did not return a response”

This means that while the sub-workflow is executed, the expected output isn’t making it back to the main agent consistently. In other words, the response payload the main agent needs isn’t present (or isn’t in the correct format) when the call to the second tool (serp_retriever) is made. This intermittent behavior can make troubleshooting difficult because the sub-workflow itself appears to have executed without errors.

Potential Causes

Some items to double-check in your setup include:

• Output Format:
  Make sure that the serp_retriever sub-workflow is returning a response in the expected format. If it’s not sending back any data (or returns a null/empty output), the main agent will display the error.

• Data Flow:
  Verify that the output from the sub-workflow is properly mapped and available to the AI agent. Sometimes, even if the sub-workflow execution succeeds, an incorrect or missing mapping of output fields can lead to the error.

• Timing or Race Conditions:
  Given that the error is intermittent, consider if there is any timing issue that might cause the main agent to call for a response before the sub-workflow has fully completed returning data.

Troubleshooting Steps

1. Check Final Output Node:
   Confirm that the sub-workflow contains a node (such as a “Set” or “Return” node) that outputs a valid JSON payload which the main workflow expects.

2. Validate Field Names:
   Ensure the field names (like chatInput or any custom fields) are correctly referenced both in the sub-workflow and in the main agent’s tool call configuration. Misnamed or missing fields might cause a null response.

3. Inspect Execution Logs:
   Even though the sub-workflow logs indicate success, review the actual output data. Try adding a temporary “Set” or “Logger” node at the end of the sub-workflow to log its final output, confirming that it matches what the main agent expects.

4. Simplify the Flow (if possible):
   As a test, simplify your sub-workflow to just return a static response. If the error goes away, you can gradually add complexity back in until you isolate the problematic part.

Summary

The error message

“The workflow did not return a response”

indicates that the main AI agent did not receive a valid output payload from the serp_retriever sub-workflow. Even though the sub-workflow itself completes, make sure its final output is properly formatted and available to be sent back to the main workflow.

Following the troubleshooting steps above should help narrow down why the output is intermittently missing or misformatted.