REST API - metadata.description - validation_error

I’m having issues implementing the metadata for a KB article

# Con metadata.description → FAIL
curl POST knowledge-base.article.create
body: { ..., "metadata": { "description": "texto..." } }
→ {"ok":false,"error":"validation_error","message":"article.content.metadata"}

# Sin metadata → OK
curl POST knowledge-base.article.create  
body: { ... }  # sin metadata
→ {"ok":true,...}