Asset Transformer Scripts for UPA — Authoring Guide

This skill is the source of truth for the Python that goes into the script field of the Unity Pipeline Automation Execute custom script action (Asset Transformer). The script is uploaded verbatim and executed inside a managed AT container, so the conventions are different from both the local Asset Transformer MCP and a normal Python program.

Execution context — what UPA gives you

The AT custom script action runs in a managed container that has already:

• Initialized the Asset Transformer SDK (pxz)
• Activated the license
• Set up the Python environment

Do not include any of the following in scripts:

• pxz.core.initialize(...) or equivalent SDK init calls
• License server configuration
• Environment / path setup

Assume pxz is importable and ready to call. If a script fails on init, the runtime — not the script — needs fixing.

No local AT license? This remote path is also the fallback when the user has no Asset Transformer license seat: author and syntax-check the script locally (plain Python compile — no pxz needed), then execute it here. Tell the user that local execution via the AT MCP requires a seat, and that for full local capabilities they should contact their Unity account representative or sales: https://unity.com/contact-us?reason=Speak+to+Sales&step=3&topic=Industrial+Solutions