diff --git a/actions-languageservice/src/complete.expressions.test.ts b/actions-languageservice/src/complete.expressions.test.ts
index a098a9d..6b5e41b 100644
--- a/actions-languageservice/src/complete.expressions.test.ts
+++ b/actions-languageservice/src/complete.expressions.test.ts
@@ -706,4 +706,20 @@ jobs:
     expect(github!.kind).toBe(CompletionItemKind.Variable);
     expect(github!.insertText).toBeUndefined();
   });
+
+  it("function parentheses are not inserted when parentheses already exist", async () => {
+    const input = `
+    on: push
+
+    jobs:
+      test:
+        runs-on: ubuntu-latest
+        steps:
+          - run: echo \${{ toJS|(github.event) }}
+    `;
+
+    const result = await complete(...getPositionFromCursor(input), undefined, contextProviderConfig);
+
+    expect(result.find(x => x.label === "toJson")!.insertText).toBe("toJson");
+  });
 });
diff --git a/actions-languageservice/src/complete.ts b/actions-languageservice/src/complete.ts
index cecfb5b..0477b19 100644
--- a/actions-languageservice/src/complete.ts
+++ b/actions-languageservice/src/complete.ts
@@ -1,4 +1,5 @@
 import {complete as completeExpression} from "@github/actions-expressions";
+import {CompletionItem as ExpressionCompletionItem} from "@github/actions-expressions/completion";
 import {convertWorkflowTemplate, isSequence, isString, parseWorkflow} from "@github/actions-workflow-parser";
 import {ErrorPolicy} from "@github/actions-workflow-parser/model/convert";
 import {DefinitionType} from "@github/actions-workflow-parser/templates/schema/definition-type";
@@ -87,13 +88,9 @@ export async function complete(
       const allowedContext = token.definitionInfo?.allowedContext || [];
       const context = await getContext(allowedContext, contextProviderConfig, workflowContext, Mode.Completion);
 
-      return completeExpression(expressionInput, context, []).map(item => {
-        return {
-          label: item.label,
-          insertText: item.function ? item.label + "()" : undefined,
-          kind: item.function ? CompletionItemKind.Function : CompletionItemKind.Variable
-        };
-      });
+      return completeExpression(expressionInput, context, []).map(item =>
+        mapExpressionCompletionItem(item, currentInput[relCharPos])
+      );
     }
   }
 
@@ -198,3 +195,17 @@ function filterAndSortCompletionOptions(options: Value[], existingValues?: Set<s
   options.sort((a, b) => a.label.localeCompare(b.label));
   return options;
 }
+
+function mapExpressionCompletionItem(item: ExpressionCompletionItem, charAfterPos: string): CompletionItem {
+  let insertText: string | undefined;
+  // Insert parentheses if the cursor is after a function
+  // and the function does not have any parantheses already
+  if (item.function) {
+    insertText = charAfterPos === "(" ? item.label : item.label + "()";
+  }
+  return {
+    label: item.label,
+    insertText: insertText,
+    kind: item.function ? CompletionItemKind.Function : CompletionItemKind.Variable
+  };
+}