diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index c16bdeeecd..13ad3af97d 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -164,9 +164,7 @@ repos:
     name: Validate configuration has default values and that each field has a docstring
     entry: python tools/validate_config.py
     language: python
-    types: [python]
-    pass_filenames: true
-    files: vllm/config.py|tests/test_config.py|vllm/entrypoints/openai/cli_args.py
+    additional_dependencies: [regex]
   # Keep `suggestion` last
   - id: suggestion
     name: Suggestion
diff --git a/tools/validate_config.py b/tools/validate_config.py
index 8b1e955c65..f6439fa9ad 100644
--- a/tools/validate_config.py
+++ b/tools/validate_config.py
@@ -9,6 +9,8 @@ import ast
 import inspect
 import sys
 
+import regex as re
+
 
 def get_attr_docs(cls_node: ast.ClassDef) -> dict[str, str]:
     """
@@ -88,11 +90,12 @@ def validate_class(class_node: ast.ClassDef):
     for stmt in class_node.body:
         # A field is defined as a class variable that has a type annotation.
         if isinstance(stmt, ast.AnnAssign):
-            # Skip ClassVar
+            # Skip ClassVar and InitVar
             # see https://docs.python.org/3/library/dataclasses.html#class-variables
-            if isinstance(stmt.annotation, ast.Subscript) and isinstance(
-                    stmt.annotation.value,
-                    ast.Name) and stmt.annotation.value.id == "ClassVar":
+            # and https://docs.python.org/3/library/dataclasses.html#init-only-variables
+            if (isinstance(stmt.annotation, ast.Subscript)
+                    and isinstance(stmt.annotation.value, ast.Name)
+                    and stmt.annotation.value.id in {"ClassVar", "InitVar"}):
                 continue
 
             if isinstance(stmt.target, ast.Name):
@@ -132,7 +135,7 @@ def validate_ast(tree: ast.stmt):
 
 def validate_file(file_path: str):
     try:
-        print(f"validating {file_path} config dataclasses ", end="")
+        print(f"Validating {file_path} config dataclasses ", end="")
         with open(file_path, encoding="utf-8") as f:
             source = f.read()
 
@@ -140,7 +143,7 @@ def validate_file(file_path: str):
         validate_ast(tree)
     except ValueError as e:
         print(e)
-        SystemExit(2)
+        raise SystemExit(1) from e
     else:
         print("✅")
 
@@ -151,7 +154,13 @@ def fail(message: str, node: ast.stmt):
 
 def main():
     for filename in sys.argv[1:]:
-        validate_file(filename)
+        # Only run for Python files in vllm/ or tests/
+        if not re.match(r"^(vllm|tests)/.*\.py$", filename):
+            continue
+        # Only run if the file contains @config
+        with open(filename, encoding="utf-8") as f:
+            if "@config" in f.read():
+                validate_file(filename)
 
 
 if __name__ == "__main__":
diff --git a/vllm/config/__init__.py b/vllm/config/__init__.py
index 69ab5712d4..25daca00c0 100644
--- a/vllm/config/__init__.py
+++ b/vllm/config/__init__.py
@@ -450,6 +450,8 @@ class ModelConfig:
 
     # Multimodal config and init vars
     multimodal_config: Optional[MultiModalConfig] = None
+    """Configuration for multimodal model. If `None`, this will be inferred
+    from the architecture of `self.model`."""
     limit_mm_per_prompt: InitVar[Optional[dict[str, int]]] = None
     media_io_kwargs: InitVar[Optional[dict[str, dict[str, Any]]]] = None
     mm_processor_kwargs: InitVar[Optional[dict[str, Any]]] = None