diff --git a/tools/spec.py b/tools/spec.py
index dce02ab..787f879 100644
--- a/tools/spec.py
+++ b/tools/spec.py
@@ -220,6 +220,9 @@ class bitmask(type):
 
 
 class handle(type):
+    parents: List[str]
+    type: str
+
     def __init__(self, node):
         assert node.tag == 'type'
         assert node.attrib['category'] == 'handle'
@@ -229,7 +232,11 @@ class handle(type):
 
         super().__init__(name, depends=[type])
         self.type = type
-        self.parent = node.attrib.get('parent', None)
+
+        parents = node.attrib.get('parent', None)
+        self.parents = parents.split(',') if parents else []
+
+        assert type
 
     def declare(self):
         return "struct %(name)s_t; using %(name)s = %(name)s_t*;" % {
@@ -244,12 +251,18 @@ class handle(type):
         assert name
         assert reg
 
-        if not self.parent:
-            return False
-        if self.parent == name:
+        if self.name == name:
             return True
 
-        return reg.types[self.parent].has_parent(name, reg)
+        if not self.parents:
+            return False
+        if name in self.parents:
+            return True
+
+        for p in self.parents:
+            if reg.types[p].has_parent(name, reg):
+                return True
+        return False
 
 
 class enum(type):
@@ -432,7 +445,7 @@ class command(type):
             self.depends += p.depends
 
     def declare(self):
-        return "%(result)s %(name)s (%(params)s) noexcept;" % {
+        return 'extern "C" %(result)s %(name)s (%(params)s) noexcept;' % {
             'name': rename(self.name),
             'result': self.result,
             'params': ", ".join(p.param for p in self.params)
@@ -773,13 +786,45 @@ if __name__ == '__main__':
 
     with open(args.dst, 'w') as dst:
         dst.write("#pragma once\n")
-        dst.write('extern "C" {\n')
         for obj in q:
             dst.write(obj.declare())
             dst.write('\n')
             dst.write(obj.define(reg))
             dst.write('\n')
-        dst.write('}\n')
+
+
+        dst.write("""
+        #include <type_traits>
+        
+        template <typename NativeT>
+        struct is_instance:
+            public std::false_type
+        {};
+        
+        template <typename NativeT>
+        struct is_device:
+            public std::false_type
+        {};
+        
+        
+        template <typename T>
+        constexpr auto is_instance_v = is_instance<T>::value;
+        
+        template <typename T>
+        constexpr auto is_device_v = is_device<T>::value;
+        """)
+
+        for obj in q:
+            if not isinstance(obj,handle):
+                continue
+
+            device_value = "true_type" if obj.has_parent("VkDevice", reg) else "false_type"
+            instance_value = "true_type" if obj.has_parent("VkInstance", reg) else "false_type"
+
+            dst.write(f"""
+            template <> struct is_instance<{obj.name}>: public std::{instance_value} {{ }};
+            template <> struct is_device<{obj.name}>: public std::{device_value} {{ }};
+            """)
 
     with open(args.icd, 'w') as icd:
         commands = [i for i in q if isinstance(i, command)]
@@ -798,7 +843,7 @@ if __name__ == '__main__':
         #define MAP_DEVICE_COMMANDS(FUNC) MAP0(FUNC,{",".join(i.name for i in device_commands)})
 
         namespace cruft::vk::icd {{
-        struct vendor;
+        class vendor;
 
         struct func {{
             void *handle;
@@ -828,7 +873,7 @@ if __name__ == '__main__':
 
     with open(args.dispatch, 'w') as dispatch:
         dispatch.write("""
-        #include "vk.hpp"
+        #include "../vk.hpp"
         #include "vtable.hpp"
 
         #include <cruft/util/debug.hpp>
@@ -840,20 +885,37 @@ if __name__ == '__main__':
         """)
 
         for obj in commands:
-            if obj.is_instance(reg):
-                table = "i_table"
-            elif obj.is_device(reg):
-                table = "d_table"
+            first_arg = reg.types[obj.params[0].type]
+
+            if not isinstance(first_arg, handle):
+                dispatch.write(f"""
+                extern "C" {obj.result} {rename(obj.name)} ({", ".join(p.param for p in obj.params)}) noexcept {{
+                    unimplemented ();
+                }}""")
+                continue
+
+            if first_arg.has_parent('VkDevice', reg):
+                table = "d_table";
+            elif first_arg.has_parent('VkInstance', reg):
+                table = 'i_table'
             else:
-                raise Exception("unhandled command type")
+                raise Exception("Unknown param type")
+
 
             dispatch.write(f"""
             extern "C" {obj.result} {rename(obj.name)} ({", ".join(p.param for p in obj.params)}) noexcept {{
-                auto const entry = reinterpret_cast<cruft::vk::icd::func const*> ({obj.params[0].name});
-                auto const *table = reinterpret_cast<decltype({table})> (entry->table);
+                using first_arg_t = std::decay_t<decltype({obj.params[0].name})>;
+            
+                if constexpr (is_instance_v<first_arg_t>) {{
+                    auto const entry = reinterpret_cast<cruft::vk::icd::func const*> ({obj.params[0].name});
+                    auto const *table = reinterpret_cast<decltype({table})> (entry->table);
 
-                return (table->{obj.name})(
-                    reinterpret_cast<decltype({obj.params[0].name})> (entry->handle),
-                    {", ".join(p.name for p in obj.params[1:])}
-                );
+                    return (table->{obj.name})(
+                        reinterpret_cast<decltype({obj.params[0].name})> (entry->handle)
+                        {", ".join([''] + [p.name for p in obj.params[1:]])}
+                    );
+                }} else {{
+                    unimplemented ();
+                }}
+            }}
             """)