diff --git a/noir-projects/aztec-nr/aztec/src/macros/dispatch.nr b/noir-projects/aztec-nr/aztec/src/macros/dispatch.nr
index 61f0f50eef23..40536b8f999d 100644
--- a/noir-projects/aztec-nr/aztec/src/macros/dispatch.nr
+++ b/noir-projects/aztec-nr/aztec/src/macros/dispatch.nr
@@ -1,4 +1,4 @@
-use super::utils::compute_fn_selector;
+use super::utils::{compute_fn_selector, size_in_fields};
 use poseidon::poseidon2::Poseidon2Hasher;
 use std::{collections::umap::UHashMap, hash::BuildHasherDefault, panic};
 
@@ -119,83 +119,6 @@ pub comptime fn generate_public_dispatch(m: Module) -> Quoted {
     }
 }
 
-comptime fn size_in_fields(typ: Type) -> u32 {
-    let size = array_size_in_fields(typ);
-    let size = size.or_else(|| bool_size_in_fields(typ));
-    let size = size.or_else(|| constant_size_in_fields(typ));
-    let size = size.or_else(|| field_size_in_fields(typ));
-    let size = size.or_else(|| int_size_in_fields(typ));
-    let size = size.or_else(|| str_size_in_fields(typ));
-    let size = size.or_else(|| struct_size_in_fields(typ));
-    let size = size.or_else(|| tuple_size_in_fields(typ));
-    if size.is_some() {
-        size.unwrap()
-    } else {
-        panic(f"Can't determine size in fields of {typ}")
-    }
-}
-
-comptime fn array_size_in_fields(typ: Type) -> Option<u32> {
-    typ.as_array().and_then(|typ: (Type, Type)| {
-        let (typ, element_size) = typ;
-        element_size.as_constant().map(|x: u32| x * size_in_fields(typ))
-    })
-}
-
-comptime fn bool_size_in_fields(typ: Type) -> Option<u32> {
-    if typ.is_bool() {
-        Option::some(1)
-    } else {
-        Option::none()
-    }
-}
-
-comptime fn field_size_in_fields(typ: Type) -> Option<u32> {
-    if typ.is_field() {
-        Option::some(1)
-    } else {
-        Option::none()
-    }
-}
-
-comptime fn int_size_in_fields(typ: Type) -> Option<u32> {
-    if typ.as_integer().is_some() {
-        Option::some(1)
-    } else {
-        Option::none()
-    }
-}
-
-comptime fn constant_size_in_fields(typ: Type) -> Option<u32> {
-    typ.as_constant()
-}
-
-comptime fn str_size_in_fields(typ: Type) -> Option<u32> {
-    typ.as_str().map(|typ| size_in_fields(typ))
-}
-
-comptime fn struct_size_in_fields(typ: Type) -> Option<u32> {
-    typ.as_data_type().map(|typ: (TypeDefinition, [Type])| {
-        let struct_type = typ.0;
-        let generics = typ.1;
-        let mut size = 0;
-        for field in struct_type.fields(generics) {
-            size += size_in_fields(field.1);
-        }
-        size
-    })
-}
-
-comptime fn tuple_size_in_fields(typ: Type) -> Option<u32> {
-    typ.as_tuple().map(|types: [Type]| {
-        let mut size = 0;
-        for typ in types {
-            size += size_in_fields(typ);
-        }
-        size
-    })
-}
-
 comptime fn get_type<T>() -> Type {
     let t: T = std::mem::zeroed();
     std::meta::type_of(t)
diff --git a/noir-projects/aztec-nr/aztec/src/macros/functions/call_interface_stubs.nr b/noir-projects/aztec-nr/aztec/src/macros/functions/call_interface_stubs.nr
index b0b9cbe4cd37..0909e93491d1 100644
--- a/noir-projects/aztec-nr/aztec/src/macros/functions/call_interface_stubs.nr
+++ b/noir-projects/aztec-nr/aztec/src/macros/functions/call_interface_stubs.nr
@@ -1,5 +1,6 @@
 use crate::macros::utils::{
     add_to_field_slice, AsStrQuote, compute_fn_selector, is_fn_private, is_fn_public, is_fn_view,
+    size_in_fields,
 };
 use std::meta::{type_of, unquote};
 
@@ -100,9 +101,10 @@ comptime fn create_private_stub(f: FunctionDefinition) -> Quoted {
     let (fn_name, fn_parameters_list, serialized_args_slice_construction, fn_name_str, fn_name_len, fn_selector) =
         create_stub_base(f);
     let fn_return_type = f.return_type();
+    let size = size_in_fields(fn_return_type);
 
     quote {
-        pub fn $fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::PrivateCallInterface<$fn_name_len, $fn_return_type, _> {
+        pub fn $fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::PrivateCallInterface<$fn_name_len, $fn_return_type, $size> {
             $serialized_args_slice_construction
             let selector = $FROM_FIELD($fn_selector);
             dep::aztec::context::call_interfaces::PrivateCallInterface::new(
@@ -120,9 +122,10 @@ comptime fn create_private_static_stub(f: FunctionDefinition) -> Quoted {
     let (fn_name, fn_parameters_list, serialized_args_slice_construction, fn_name_str, fn_name_len, fn_selector) =
         create_stub_base(f);
     let fn_return_type = f.return_type();
+    let size = size_in_fields(fn_return_type);
 
     quote {
-        pub fn $fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::PrivateStaticCallInterface<$fn_name_len, $fn_return_type, _> {
+        pub fn $fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::PrivateStaticCallInterface<$fn_name_len, $fn_return_type, $size> {
             $serialized_args_slice_construction
             let selector = $FROM_FIELD($fn_selector);
             dep::aztec::context::call_interfaces::PrivateStaticCallInterface::new(
@@ -176,9 +179,10 @@ comptime fn create_public_stub(f: FunctionDefinition) -> Quoted {
     let (fn_name, fn_parameters_list, serialized_args_slice_construction, fn_name_str, fn_name_len, fn_selector) =
         create_stub_base(f);
     let fn_return_type = f.return_type();
+    let size = size_in_fields(fn_return_type);
 
     quote {
-        pub fn $fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::PublicCallInterface<$fn_name_len, $fn_return_type, _> {
+        pub fn $fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::PublicCallInterface<$fn_name_len, $fn_return_type, $size> {
             $serialized_args_slice_construction
             let selector = $FROM_FIELD($fn_selector);
             dep::aztec::context::call_interfaces::PublicCallInterface::new(
@@ -196,9 +200,10 @@ comptime fn create_public_static_stub(f: FunctionDefinition) -> Quoted {
     let (fn_name, fn_parameters_list, serialized_args_slice_construction, fn_name_str, fn_name_len, fn_selector) =
         create_stub_base(f);
     let fn_return_type = f.return_type();
+    let size = size_in_fields(fn_return_type);
 
     quote {
-        pub fn $fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::PublicStaticCallInterface<$fn_name_len, $fn_return_type, _> {
+        pub fn $fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::PublicStaticCallInterface<$fn_name_len, $fn_return_type, $size> {
             $serialized_args_slice_construction
             let selector = $FROM_FIELD($fn_selector);
             dep::aztec::context::call_interfaces::PublicStaticCallInterface::new(
@@ -252,12 +257,13 @@ comptime fn create_utility_stub(f: FunctionDefinition) -> Quoted {
     let (fn_name, fn_parameters_list, serialized_args_slice_construction, fn_name_str, fn_name_len, fn_selector) =
         create_stub_base(f);
     let fn_return_type = f.return_type();
+    let size = size_in_fields(fn_return_type);
 
     // This is here because utility function call interfaces can only be used within TXe tests.
     let modified_fn_name = f"_experimental_{fn_name}".quoted_contents();
 
     quote {
-        pub fn $modified_fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::UtilityCallInterface<$fn_name_len, $fn_return_type, _> {
+        pub fn $modified_fn_name(self, $fn_parameters_list) -> dep::aztec::context::call_interfaces::UtilityCallInterface<$fn_name_len, $fn_return_type, $size> {
             $serialized_args_slice_construction
             let selector = $FROM_FIELD($fn_selector);
             dep::aztec::context::call_interfaces::UtilityCallInterface::new(
diff --git a/noir-projects/aztec-nr/aztec/src/macros/utils.nr b/noir-projects/aztec-nr/aztec/src/macros/utils.nr
index a8b0383aadc5..75da12ac9494 100644
--- a/noir-projects/aztec-nr/aztec/src/macros/utils.nr
+++ b/noir-projects/aztec-nr/aztec/src/macros/utils.nr
@@ -288,3 +288,76 @@ pub(crate) comptime fn get_trait_impl_method(
         .filter(|m| m.name() == target_method)[0]
         .as_typed_expr()
 }
+
+pub comptime fn size_in_fields(typ: Type) -> u32 {
+    array_size_in_fields(typ)
+        .or_else(|| bool_size_in_fields(typ))
+        .or_else(|| constant_size_in_fields(typ))
+        .or_else(|| field_size_in_fields(typ))
+        .or_else(|| int_size_in_fields(typ))
+        .or_else(|| str_size_in_fields(typ))
+        .or_else(|| struct_size_in_fields(typ))
+        .or_else(|| tuple_size_in_fields(typ))
+        .expect(f"Can't determine size in fields of {typ}")
+}
+
+comptime fn array_size_in_fields(typ: Type) -> Option<u32> {
+    typ.as_array().and_then(|typ: (Type, Type)| {
+        let (typ, element_size) = typ;
+        element_size.as_constant().map(|x: u32| x * size_in_fields(typ))
+    })
+}
+
+comptime fn bool_size_in_fields(typ: Type) -> Option<u32> {
+    if typ.is_bool() {
+        Option::some(1)
+    } else {
+        Option::none()
+    }
+}
+
+comptime fn field_size_in_fields(typ: Type) -> Option<u32> {
+    if typ.is_field() {
+        Option::some(1)
+    } else {
+        Option::none()
+    }
+}
+
+comptime fn int_size_in_fields(typ: Type) -> Option<u32> {
+    if typ.as_integer().is_some() {
+        Option::some(1)
+    } else {
+        Option::none()
+    }
+}
+
+comptime fn constant_size_in_fields(typ: Type) -> Option<u32> {
+    typ.as_constant()
+}
+
+comptime fn str_size_in_fields(typ: Type) -> Option<u32> {
+    typ.as_str().map(|typ| size_in_fields(typ))
+}
+
+comptime fn struct_size_in_fields(typ: Type) -> Option<u32> {
+    typ.as_data_type().map(|typ: (TypeDefinition, [Type])| {
+        let struct_type = typ.0;
+        let generics = typ.1;
+        let mut size = 0;
+        for field in struct_type.fields(generics) {
+            size += size_in_fields(field.1);
+        }
+        size
+    })
+}
+
+comptime fn tuple_size_in_fields(typ: Type) -> Option<u32> {
+    typ.as_tuple().map(|types: [Type]| {
+        let mut size = 0;
+        for typ in types {
+            size += size_in_fields(typ);
+        }
+        size
+    })
+}