Need help with “Call n8n Workflow Tool” error

[b-ub]

Hey everyone,

my AI agent is able to trigger the “Call n8n Workflow Tool,” but I keep getting an error. The screenshots show an agent that should generate an image. It works with a Telegram trigger, but not via the AI tool.

Settings:

• Input: Agent should use the tool
• Tool: Source = “Database,” correct workflow selected
• Trigger: “Executed by another Workflow” with “Accept all data”
• Naming: Request and nodes are correctly named
• Version: Using the cloud version

Any idea what might be causing the issue? Thanks a lot in advance!

[solomon]

It is good practice to specify the input your subworkflow is going to accept.
“Accept all data” leaves it open for all kinds of structure that could lead to errors.

Try something like this:

AI Agent

Subworkflow

.
See how I have limited the type of data that gets into the subworkflow?
Also notice the $fromAI function I’ve used in the tool.

If my reply answers your question, please remember to mark it as a solution.

[b-ub]

@solomon

See how I have limited the type of data that gets into the subworkflow?
Also notice the $fromAI function I’ve used in the tool.

If my reply answers your question, please remember to mark it as a solution.

Hi Solomon,
Thanks so much for your support! Unfortunately, the sub-workflow still isn’t being triggered. Any other idea what might be causing it?

[solomon]

Hey @b-ub,

I see you are not using an expression in that field.
Instead you are using a Fixed text.

To enable the expression, hover over the text field and you will see two small tabs that pop-up:

• Fixed
• Expression

Click expression to enable it

[b-ub]

@solomon

I see you are not using an expression in that field.
Instead you are using a Fixed text.

To enable the expression, hover over the text field and you will see two small tabs that pop-up:

• Fixed
• Expression

Click expression to enable it

It’s still not working, unfortunately – but I think we’re on the right track! Do you have another idea we could try? Thanks a lot!

[solomon]

The error message indicates that the workflow executed twice—once for each item. On the second item, however, the Telegram Trigger didn’t fire.

This suggests that you are passing more items downstream than the Telegram Trigger is actually triggering.

[b-ub]

@solomon

The error message indicates that the workflow executed twice—once for each item. On the second item, however, the Telegram Trigger didn’t fire.

This suggests that you are passing more items downstream than the Telegram Trigger is actually triggering.

The multiple trigger issue is fixed – yay!

But the tool still isn’t being triggered. Any other idea we could try? Thanks a lot!

[solomon]

Can you please go into the execution that triggered the error and see where it’s happening, please?

You have to enter the subworkflow and check its executions.

[b-ub]

Thanks to your last message, I found and fixed the issue. Really appreciate it!