diff --git a/builtin.py b/builtin.py
index 520e483c..e388fd7b 100644
--- a/builtin.py
+++ b/builtin.py
@@ -378,6 +378,8 @@ def parse_function_doc(func):
         end = 0
         param_str = ''
 
+    param_str = param_str.replace('-', '_')  # see: isinstance.__doc__
+
     if doc is not None:
         r = re.search('-[>-]* ', doc[end:end + 7])
     if doc is None or r is None:
diff --git a/functions.py b/functions.py
index 0d5bea98..0369f925 100644
--- a/functions.py
+++ b/functions.py
@@ -13,7 +13,7 @@ import keywords
 from _compatibility import next
 
 __all__ = ['complete', 'goto', 'get_definition', 'related_names',
-           'NotFoundError', 'set_debug_function']
+           'NotFoundError', 'set_debug_function', 'get_in_function_call']
 
 
 class NotFoundError(Exception):
@@ -112,6 +112,29 @@ class Definition(dynamic.BaseOutput):
         return "%s:%s%s" % (self.module_name, self.description, position)
 
 
+class CallDef(object):
+    def __init__(self, executable, index):
+        self.executable = executable
+        self.index = index
+
+    @property
+    def params(self):
+        if isinstance(self.executable, evaluate.Function):
+            return self.executable.params
+        else:
+            try:
+                sub = self.executable.get_subscope_by_name('__init__')
+                return sub.params
+            except KeyError:
+                print self.executable.subscopes
+                print 'LALA'
+                return []
+
+    def __repr__(self):
+        return '<%s: %s index %s>' % (self.__class__.__name__, self.executable,
+                                    self.index)
+
+
 def _get_completion_parts(path):
     """
     Returns the parts for the completion
@@ -173,8 +196,10 @@ def complete(source, line, column, source_path):
     needs_dot = not dot and path
     c = [Completion(c, needs_dot, len(like), s) for c, s in set(completions)]
 
+    call_def = _get_in_function_call(f, pos)
+
     _clear_caches()
-    return c
+    return c, call_def
 
 
 def _prepare_goto(position, source_path, module, goto_path,
@@ -365,3 +390,54 @@ def set_debug_function(func_cb):
 
 def _clear_caches():
     evaluate.clear_caches()
+
+def get_in_function_call(source, line, column, source_path):
+    pos = (line, column)
+    f = modules.ModuleWithCursor(source_path, source=source, position=pos)
+
+    return _get_in_function_call(f, pos)
+
+def _get_in_function_call(module, pos):
+    def scan_array_for_pos(arr, pos):
+        """ Returns the function Call that match search_name in an Array. """
+        index = None
+        call = None
+        for index, sub in enumerate(arr):
+            call = None
+            for s in sub:
+                if isinstance(s, parsing.Array):
+                    new = scan_array_for_pos(s, pos)
+                    if new[0] is not None:
+                        call, index = new
+                elif isinstance(s, parsing.Call):
+                    while s is not None:
+                        if s.start_pos >= pos:
+                            return call, index
+                        if s.execution is not None:
+                            if s.execution.start_pos <= pos:
+                                call = s
+                            else:
+                                return call, index
+                            c, index = scan_array_for_pos(s.execution, pos)
+                            if c is not None:
+                                call = c
+                        s = s.next
+        return call, index
+
+    user_stmt = module.parser.user_stmt
+    if user_stmt is None:
+        return None
+    ass = user_stmt.get_assignment_calls()
+
+    call, index = scan_array_for_pos(ass, pos)
+    if call is None:
+        return None
+
+    call.execution, temp = None, call.execution
+    origins = evaluate.follow_call(call)
+    call.execution = temp
+
+    if len(origins) == 0:
+        return None
+    executable = origins[0]  # just take entry zero, because we need just one.
+    return CallDef(executable, index)
diff --git a/parsing.py b/parsing.py
index a9bea4b8..8c5db7c6 100644
--- a/parsing.py
+++ b/parsing.py
@@ -298,6 +298,9 @@ class Module(Scope):
             self._name = Name(names, self.start_pos, self.end_pos, self)
         return self._name
 
+    def is_builtin(self):
+        return not self.path.endswith('.py')
+
 
 class Class(Scope):
     """
diff --git a/plugin/jedi.vim b/plugin/jedi.vim
index d4b83b76..29e91621 100644
--- a/plugin/jedi.vim
+++ b/plugin/jedi.vim
@@ -45,7 +45,7 @@ if 1:
         # here again, the hacks, because jedi has a different interface than vim
         column += len(base)
         try:
-            completions = functions.complete(source, row, column, buf_path)
+            completions, call_def = functions.complete(source, row, column, buf_path)
             out = []
             for c in completions:
                 d = dict(word=c.word[:len(base)] + c.complete,
@@ -64,9 +64,10 @@ if 1:
             print(traceback.format_exc())
             strout = ''
             completions = []
+            call_def = None
 
         #print 'end', strout
-        show_func_def(len(completions))
+        show_func_def(call_def, len(completions))
         vim.command('return ' + strout)
 PYTHONEOF
 endfunction
@@ -459,7 +460,8 @@ def _goto(is_definition=False, is_related_name=False, no_output=False):
             vim.command('call <sid>add_goto_window()')
     return definitions
 
-def show_func_def(completion_lines=0):
+
+def show_func_def(call_def, completion_lines=0):
     row, column = vim.current.window.cursor
     vim.eval('jedi#clear_func_def()')
 
@@ -470,6 +472,8 @@ def show_func_def(completion_lines=0):
     line = vim.eval("getline(%s)" % row_to_replace)
 
     insert_column = column - 2 # because it has stuff at the beginning
+
+    print call_def, call_def.params
     text = " (*asdf*, basdf) "
     text = ' ' * (insert_column - len(line)) + text
     end_column = insert_column + len(text) - 2  # -2 because of bold symbols
diff --git a/test/regression.py b/test/regression.py
index 0f35e508..510d06e2 100755
--- a/test/regression.py
+++ b/test/regression.py
@@ -18,6 +18,11 @@ class TestRegression(unittest.TestCase):
     def complete(self, src, pos):
         return functions.complete(src, pos[0], pos[1], '')
 
+    def get_in_function_call(self, src, pos=None):
+        if pos is None:
+            pos = 1, len(src)
+        return functions.get_in_function_call(src, pos[0], pos[1], '')
+
     def test_get_definition_cursor(self):
 
         s = ("class A():\n"
@@ -100,6 +105,16 @@ class TestRegression(unittest.TestCase):
              )
         functions.related_names(s, 2, 2, '/')
 
+    def test_get_in_function_call(self):
+        s = "isinstance(a, abs("
+        s2 = "isinstance(), "
+        print
+        check = lambda call_def, index: call_def and call_def.index == index
+        assert check(self.get_in_function_call(s, (1,11)), 0)
+        assert check(self.get_in_function_call(s, (1,14)), 1)
+        assert check(self.get_in_function_call(s, (1,15)), 1)
+        assert check(self.get_in_function_call(s, (1,18)), 0)
+        assert self.get_in_function_call(s2) is None
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/test/run.py b/test/run.py
index 77cf9b71..8b80e3ad 100755
--- a/test/run.py
+++ b/test/run.py
@@ -24,7 +24,8 @@ def run_completion_test(correct, source, line_nr, index, line, path):
     # lines start with 1 and column is just the last (makes no
     # difference for testing)
     try:
-        completions = functions.complete(source, line_nr, index, path)
+        completions, call_def = functions.complete(source, line_nr, index,
+                                                                        path)
         #import cProfile as profile
         #profile.run('functions.complete("""%s""", %i, %i, "%s")'
         #                            % (source, line_nr, len(line), path))