diff --git a/src/lib.rs b/src/lib.rs
index c3a580d..ea3a708 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -558,9 +558,9 @@ impl MessageBehavior for VmcExtKey {
             args,
         };
     }
-    fn from_osc_message(msg: OscMessage) -> Result<Self, String> {
+    fn from_osc_message(msg: OscMessage) -> Result<Self, FromMessageErr> {
         if msg.args.len() != 3 {
-            return Err(String::from("arg count invalid"));
+            return Err(FromMessageErr::ArgCount(ArgCountErr { expected_in: vec![3], actual: msg.args.len(), addr: msg.addr}));
         }
         let active: bool;
         let name: String;
@@ -572,18 +572,18 @@ impl MessageBehavior for VmcExtKey {
                 } else if i == 0 {
                     active = false;
                 } else {
-                    return Err(String::from("arg value invalid"));
+                    return Err(FromMessageErr::IntRange(IntRangeErr { expected_lower: 0, expected_upper: 1, actual: i, addr: msg.addr, arg_count: 0}));
                 }
             }
-            _ => return Err(String::from("arg type invalid")),
+            _ => return Err(FromMessageErr::ArgType(ArgTypeErr { expected: OscType::Int(0), actual: msg.args[0], addr: msg.addr, arg_count: 0})),
         }
         match &msg.args[1] {
             OscType::String(s) => name = s.to_owned(),
-            _ => return Err(String::from("arg type invalid")),
+            _ => return Err(FromMessageErr::ArgType(ArgTypeErr { expected: OscType::String(String::new()), actual: msg.args[1], addr: msg.addr, arg_count: 1})),
         }
         match msg.args[2] {
             OscType::Int(i) => keycode = i,
-            _ => return Err(String::from("arg type invalid")),
+            _ => return Err(FromMessageErr::ArgType(ArgTypeErr { expected: OscType::Int(0), actual: msg.args[2], addr: msg.addr, arg_count: 2})),
         }
         return Ok(VmcExtKey {
             active,