diff --git a/jedi/evaluate/compiled/access.py b/jedi/evaluate/compiled/access.py
index 4e704947..20e9df30 100644
--- a/jedi/evaluate/compiled/access.py
+++ b/jedi/evaluate/compiled/access.py
@@ -377,6 +377,21 @@ class DirectObjectAccess(object):
         return inspect.isclass(self._obj) and self._obj != type
 
     def get_signature_params(self):
+        return [
+            SignatureParam(
+                name=p.name,
+                has_default=p.default is not p.empty,
+                default=self._create_access_path(p.default),
+                has_annotation=p.annotation is not p.empty,
+                annotation=self._create_access_path(p.annotation),
+                kind_name=str(p.kind)
+            ) for p in self._get_signature().parameters.values()
+        ]
+
+    def get_signature_text(self):
+        return str(self._get_signature())
+
+    def _get_signature(self):
         obj = self._obj
         if py_version < 33:
             raise ValueError("inspect.signature was introduced in 3.3")
@@ -397,22 +412,12 @@ class DirectObjectAccess(object):
                 raise ValueError
 
         try:
-            signature = inspect.signature(obj)
+            return inspect.signature(obj)
         except (RuntimeError, TypeError):
             # Reading the code of the function in Python 3.6 implies there are
             # at least these errors that might occur if something is wrong with
             # the signature. In that case we just want a simple escape for now.
             raise ValueError
-        return [
-            SignatureParam(
-                name=p.name,
-                has_default=p.default is not p.empty,
-                default=self._create_access_path(p.default),
-                has_annotation=p.annotation is not p.empty,
-                annotation=self._create_access_path(p.annotation),
-                kind_name=str(p.kind)
-            ) for p in signature.parameters.values()
-        ]
 
     def negate(self):
         return self._create_access_path(-self._obj)
diff --git a/jedi/evaluate/compiled/context.py b/jedi/evaluate/compiled/context.py
index 36f1936b..2f664b84 100644
--- a/jedi/evaluate/compiled/context.py
+++ b/jedi/evaluate/compiled/context.py
@@ -5,6 +5,7 @@ import re
 from functools import partial
 
 from jedi import debug
+from jedi.evaluate.utils import to_list
 from jedi._compatibility import force_unicode, Parameter, cast_path
 from jedi.cache import underscore_memoization, memoize_method
 from jedi.evaluate.filters import AbstractFilter
@@ -111,6 +112,7 @@ class CompiledObject(Context):
     def py__doc__(self):
         return self.access_handle.py__doc__()
 
+    @to_list
     def get_param_names(self):
         try:
             signature_params = self.access_handle.get_signature_params()
@@ -126,6 +128,13 @@ class CompiledObject(Context):
             for signature_param in signature_params:
                 yield SignatureParamName(self, signature_param)
 
+    def get_signature_text(self):
+        try:
+            return self.access_handle.get_signature_text()
+        except ValueError:
+            params_str, ret = self._parse_function_doc()
+            return '(' + params_str + ')' + ret
+
     def get_signatures(self):
         return [BuiltinSignature(self)]
 
diff --git a/jedi/evaluate/signature.py b/jedi/evaluate/signature.py
index 9b3fc2df..d5e1d9db 100644
--- a/jedi/evaluate/signature.py
+++ b/jedi/evaluate/signature.py
@@ -10,6 +10,7 @@ class AbstractSignature(object):
     def name(self):
         return self.context.name
 
+    @property
     def annotation(self):
         return None
 
@@ -34,6 +35,7 @@ class TreeSignature(AbstractSignature):
     def bind(self, context):
         return TreeSignature(context, self._function_context, is_bound=True)
 
+    @property
     def annotation(self):
         return self._function_context.tree_node.annotation
 
@@ -52,7 +54,7 @@ class BuiltinSignature(AbstractSignature):
         return self.context
 
     def to_string(self):
-        return ''
+        return self.name.string_name + self.context.get_signature_text()
 
     def bind(self, context):
         raise NotImplementedError('pls implement, need test case, %s' % context)
diff --git a/test/test_evaluate/test_signature.py b/test/test_evaluate/test_signature.py
new file mode 100644
index 00000000..7f744247
--- /dev/null
+++ b/test/test_evaluate/test_signature.py
@@ -0,0 +1,15 @@
+import pytest
+
+from jedi.evaluate.gradual.conversion import stub_to_actual_context_set
+
+
+def test_compiled_signature(Script):
+    code = 'import math; math.cos'
+    sig = 'cos(x, /)'
+    d, = Script(code).goto_definitions()
+    context, = d._name.infer()
+    compiled, = stub_to_actual_context_set(context)
+    signature, = compiled.get_signatures()
+    assert signature.to_string() == sig
+    assert signature.get_param_names() == []
+    assert signature.annotation is None