Closed — not a problem by design.
Celeste is a primitives layer. Dict tools are passed through to the provider as-is — celeste does not validate tool schemas, names, or structure. The provider API is the source of truth. ToolSupport intentionally only validates Tool instances (WebSearch, XSearch, etc.) to check model capability. Dict tools bypass this because celeste cannot and should not know all valid provider-specific tool formats.
See #218 for the philosophy statement.