I have just re-analysed most common failed tool-calls and adjusted the tool so that it works. I have a manual repair step on failure that programmatically attempts to fix some things. On failure, the harness reports the error, the repaired function, and the result. Overall, seems to work fine. But it's very model-specific. Most commonly the model fails on shell commands where it hallucinates some programs. If it does it often enough, I just promote those to commands in the PATH. Over time, it has happened less.