change

backend/agent/skills/cad-engine/SKILL.md

@@ -6,7 +6,9 @@ Help an AI agent generate CAD models through the repository's CDSL engine.
 
 ## Required workflow
 
-1. Read the engine README and the relevant engine modules.
+1. Read the engine README, `profile_schema.json`, `cdsl_schema.json`, and the
+   relevant engine modules. `cdsl_schema.json` is the executable CDSL input
+   contract; its nested object and array shapes are mandatory.
 2. Search the official CDSL library for similar parts, profiles, and feature
    sequences.
 3. Produce or revise parameterized CDSL.
@@ -20,4 +22,7 @@ Help an AI agent generate CAD models through the repository's CDSL engine.
 - Do not use `compiler_context` as the final source of missing training data.
 - Keep the generated CDSL self-sufficient whenever the supported shape
   generators can express the geometry.
+- Use only the feature operations, profile types, parameter names, and nested
+  value shapes in `cdsl_schema.json`. In particular, hole positions must be
+  objects such as `{"mm": [u_mm, v_mm, w_mm]}`, never bare coordinate arrays.
 - Preserve the original CDSL and write revisions as separate artifacts.