diff --git a/packages/data-designer-engine/pyproject.toml b/packages/data-designer-engine/pyproject.toml
index e78f6a64c..7cbda6d05 100644
--- a/packages/data-designer-engine/pyproject.toml
+++ b/packages/data-designer-engine/pyproject.toml
@@ -51,6 +51,7 @@ dependencies = [
     "mcp>=1.26.0,<2",
     "networkx>=3.0,<4",
     "numpy>=1.23.5,<3",
+    "pydantic>=2.9.2,<3",
     "pyjwt[crypto]>=2.13.0,<3", # 2.13.0 fixes PyJWT security advisories pulled in by mcp
     "python-multipart>=0.0.29,<1", # 0.0.29 addresses multipart security advisories pulled in by mcp
     "ruff>=0.14.10,<1",