Code
T7008 tools-too-deep
The flows and agents that are tools of an agent stand deeper than callDepth, or lead back to the agent. The check finds it.
Details
A flow or an agent that is a tool is a run of its own, called from the run of the one that uses it. Runs stand at most callDepth deep, 3 where project.limits states none: the call of a run one level deeper is refused with code.T5105. A tool that leads back to the agent that uses it would call it for ever.
The fix
Give the agent fewer levels of tools that are runs, raise callDepth in project.limits, or take the agent out of the tools that lead back to it.