diff --git a/gen.py b/gen.py
index d118fdc..b1e75f8 100755
--- a/gen.py
+++ b/gen.py
@@ -1,7 +1,6 @@
 #!/usr/bin/env python3
 """schema.json generator."""
-# import re
-from typing import Any, NewType
+from typing import Annotated, Any, NewType
 
 from pydantic import BaseModel, ConfigDict, Field, RootModel
 
@@ -275,12 +274,7 @@ class Stage(BaseModel):
 Parametrized stage definition that'll be substituted over for each of the \
 value from the foreach data."""
 
-
-# class ParametrizedString(ConstrainedStr):
-#     regex = re.compile(r"^\${.*?}$")
-
-# FIXME: how to add support for regex str?
-ParametrizedString = str
+ParametrizedString = Annotated[str, Field(pattern=r"^\$\{.*?\}$")]
 
 
 class ForeachDo(BaseModel):
@@ -327,11 +321,9 @@ class TopLevelPlotsList(RootModel):
     root: list[PlotIdOrFilePath | TopLevelPlots] = Field(default_factory=list)
 
 
-# class ArtifactIdOrFilePath(ConstrainedStr):
-#     regex = re.compile(r"^[a-z0-9]([a-z0-9-/]*[a-z0-9])?$")
-
-# FIXME: how to add support for regex str?
-ArtifactIdOrFilePath = str
+ArtifactIdOrFilePath = Annotated[
+    str, Field(pattern=r"^[a-z0-9]([a-z0-9-/]*[a-z0-9])?$")
+]
 
 
 class TopLevelArtifacts(RootModel):
@@ -377,9 +369,9 @@ class DvcYamlModel(BaseModel):
     )
 
     args = parser.parse_args()
+    json_data = DvcYamlModel.model_json_schema()
     # oneOf is expected by the JSON specification but union produces anyOf
     # https://github.com/pydantic/pydantic/issues/656
-    json_data = DvcYamlModel.model_json_schema()
     out = json.dumps(json_data, indent=2).replace('"anyOf"', '"oneOf"')
     args.outfile.write(out)
     args.outfile.write("\n")
diff --git a/schema.json b/schema.json
index cf3dc02..4abdd56 100644
--- a/schema.json
+++ b/schema.json
@@ -41,6 +41,7 @@
         "foreach": {
           "oneOf": [
             {
+              "pattern": "^\\$\\{.*?\\}$",
               "type": "string"
             },
             {
@@ -225,6 +226,7 @@
                 "type": "array"
               },
               {
+                "pattern": "^\\$\\{.*?\\}$",
                 "type": "string"
               }
             ]
@@ -805,8 +807,10 @@
       "type": "object"
     },
     "TopLevelArtifacts": {
-      "additionalProperties": {
-        "$ref": "#/$defs/TopLevelArtifactFlags"
+      "patternProperties": {
+        "^[a-z0-9]([a-z0-9-/]*[a-z0-9])?$": {
+          "$ref": "#/$defs/TopLevelArtifactFlags"
+        }
       },
       "title": "TopLevelArtifacts",
       "type": "object"