uefn-scripting-batch

Source: Claude/docs/mcp/scripting-batch.md, recipes.json (only tool-ok or proven; proven = the same call form already worked in real work), SKILLS-PROPOSAL.md B7.

Read first

1. Read uefn-mcp-lab-guard (the guard sees only the OUTER call, so the script itself must use lab paths only).
2. Ping with a cheap read before the first write script.
3. If the MCP does not answer: stop and report. Never close or kill a running editor (after a crash: uefn_session.py recover, opt-in).

Rules

• Paths inside scripts: GUID form /09e4e8d3-83f9-4ee0-9777-072ed3984380/root_ai_lab/...; nothing outside the lab, no other project's mount.
• The guard is not bypassed (no sandbox-escape attempts; dunder access is out of scope); a refusal is reported verbatim.
• If a recipe fails: exact error text, then STOP.
• No write script without a cleanup plan: inner errors cannot be caught and there is NO rollback, the caller deletes what was created.

Verified recipes (toolset editor_toolset.toolsets.programmatic.ProgrammaticToolset)

Tool	Args	Note
get_execution_environment	{}	returns instructions, supported_modules (json, math, datetime, copy, re, time), language python
execute_tool_script #batch_reads	script: several read tools, returns a dict	read only; timing with time
execute_tool_script #create_widget_chain	CreateWidgetBlueprint, AddWidget Overlay (parentWidget None), AddWidget StackBox, CompileWidgetBlueprint, save	cleanup: AssetTools/delete {path} of the blueprint
execute_tool_script #verse_edit_build	Replace + BuildAll, returns diagnostics	~5 s for two builds; cleanup as Replace

Script shape: define run() returning a dict; call execute_tool("<Toolset>.<Tool>", json.dumps(args))["returnValue"] (dot between toolset and tool inside scripts).

Traps (exact messages)

• Forbidden import: Import of 'os' is not permitted. Allowed modules: frozenset({'json', 'time', 'math', 'datetime', 'copy', 're'}); same for subprocess, sys, unreal.
• Script must define a callable run() function.; run() must return a dict[str, Any], returned list.
• Args as dict: TypeError: the JSON object must be str, bytes or bytearray, not dict (use json.dumps).
• A failing inner tool cannot be caught (try/except does not work); the script aborts and earlier writes stay (seen: orphan WBP_Scr007 with its Overlay).
• No state between scripts; open(..., "w") refused (Mode 'w' is not permitted); reads only in the editor's allowed directories; eval/exec are NameError.
• Before a write script check exists inside it; on failure list what was written and delete it.

To try (not verified)

• recipe/apply_material_instance_to_actor (ONE script: add actor, set overrideMaterials, read back, reset, remove): status unverified in recipes.json; materials area; apply+read+reset+remove must stay in one script.
• recipe/animate_owner_actor_with_script_and_restore: status field is unverified (the inner verified flag is inconsistent); loop of set_actor_transform with time.sleep, restores the original transform. Confirm before use.