Run existing tool runs another tool as a step in this flow. Build something once, like fetching a customer record, and reuse it in every tool that needs it. When you change the shared tool, every flow that uses it picks up the change.
Adding one
In the step menu under Reuse, pick the tool to run. You can also type a name and add it as a draft: the step is created now, and you build the draft tool later. Open tool opens the referenced tool in a new tab.
Parameters
The referenced tool's input parameters appear under Parameters. Map a value to each one; required parameters are marked with an asterisk, and each parameter's description appears on hover.
The tool's result becomes this step's output, stored in the variable you pick under Select output variable.