diff --git a/hvcc/core/json/heavy_ir.py b/hvcc/core/json/heavy_ir.py
index 1680f78..dd4850a 100644
--- a/hvcc/core/json/heavy_ir.py
+++ b/hvcc/core/json/heavy_ir.py
@@ -1,5 +1,8 @@
 from pydantic import BaseModel, RootModel
-from typing import List, Optional, Union
+from typing import List, Optional, Union, Literal
+
+
+ConnectionType = Literal["-->", "~i>", "~f>", "signal"]
 
 
 class Arg(BaseModel):
@@ -23,9 +26,9 @@ class Perf(BaseModel):
 
 
 class IRNode(BaseModel):
-    inlets: List[str]
+    inlets: List[ConnectionType]
     ir: IR
-    outlets: List[str]
+    outlets: List[ConnectionType]
     args: List[Arg] = []
     perf: Optional[Perf] = Perf()
     # perf: Perf
diff --git a/hvcc/core/json/heavy_lang.py b/hvcc/core/json/heavy_lang.py
index f378fb2..b126f1f 100644
--- a/hvcc/core/json/heavy_lang.py
+++ b/hvcc/core/json/heavy_lang.py
@@ -1,25 +1,28 @@
 from pydantic import BaseModel, RootModel
-from typing import List, Optional, Any
+from typing import List, Optional, Dict, Literal, Union
 
 
-class Inlet(BaseModel):
+ConnectionType = Literal["-->", "-~>", "~f>"]
+
+
+class Arg(BaseModel):
     name: str
-    connectionType: str
+    value_type: Optional[str]
     description: str
+    default: Union[float, int, str, Dict, List, None] = None
+    required: bool
 
 
-class Outlet(BaseModel):
+class Inlet(BaseModel):
     name: str
-    connectionType: str
+    connectionType: ConnectionType
     description: str
 
 
-class Arg(BaseModel):
+class Outlet(BaseModel):
     name: str
-    value_type: Optional[str]
+    connectionType: ConnectionType
     description: str
-    default: Any
-    required: bool
 
 
 class LangNode(BaseModel):