diff --git a/smnp/ast/node/function.py b/smnp/ast/node/function.py
index 82981cf..30bf3a4 100644
--- a/smnp/ast/node/function.py
+++ b/smnp/ast/node/function.py
@@ -103,7 +103,7 @@ def ArgumentParser(input):
 
     return Parser.allOf(
         Parser.optional(TypeParser),
-        IdentifierLiteralParser,
+        Parser.doAssert(IdentifierLiteralParser, "argument name"),
         Parser.optional(Parser.terminal(TokenType.DOTS, lambda val, pos: True)),
         createNode=createNode,
         name="function argument"
@@ -115,24 +115,26 @@ def ArgumentsDeclarationParser(input):
         ArgumentsDeclaration,
         TokenType.OPEN_PAREN,
         TokenType.CLOSE_PAREN,
-        ArgumentParser
+        Parser.doAssert(ArgumentParser, "function/method argument")
     )(input)
 
 
 def FunctionDefinitionParser(input):
     return Parser.allOf(
         Parser.terminal(TokenType.FUNCTION),
-        IdentifierLiteralParser,
-        ArgumentsDeclarationParser,
-        MethodBodyParser,
+        Parser.doAssert(IdentifierLiteralParser, "function/method name"),
+        Parser.doAssert(ArgumentsDeclarationParser, "function/method arguments"),
+        Parser.doAssert(MethodBodyParser, "function/method body"),
         createNode=lambda _, name, args, body: FunctionDefinition.withValues(name, args, body),
         name="function definition"
     )(input)
 
+
 def MethodBodyParser(input):
     bodyItem = Parser.oneOf(
-        StatementParser,
         ReturnParser,
+        StatementParser,
+        assertExpected="statement",
         name="function body item"
     )
 
diff --git a/smnp/ast/node/imports.py b/smnp/ast/node/imports.py
index b16afb9..8305cf9 100644
--- a/smnp/ast/node/imports.py
+++ b/smnp/ast/node/imports.py
@@ -27,7 +27,7 @@ class Import(Node):
 def ImportParser(input):
     return Parser.allOf(
         Parser.terminal(TokenType.IMPORT),
-        StringParser,
+        Parser.doAssert(StringParser, "import source as string"),
         createNode=lambda imp, source: Import.withValue(source),
         name="import"
     )(input)
diff --git a/smnp/token/tokenizers/note.py b/smnp/token/tokenizers/note.py
index 672d66f..6454aba 100644
--- a/smnp/token/tokenizers/note.py
+++ b/smnp/token/tokenizers/note.py
@@ -14,7 +14,7 @@ def noteTokenizer(input, current, line):
     rawValue = ''
     if input[current] == '@':
         rawValue += input[current+consumedChars]
-        consumedChars += 1
+        consumedChars += 1  # TODO: Check if next item does even exist
         if input[current+consumedChars] in ('C', 'c', 'D', 'd', 'E', 'e', 'F', 'f', 'G', 'g', 'A', 'a', 'H', 'h', 'B', 'b'):
             rawValue += input[current + consumedChars]
             notePitch = input[current+consumedChars]