diff --git a/server/gx-workflow-ls-format2/src/gxFormat2WorkflowDocument.ts b/server/gx-workflow-ls-format2/src/gxFormat2WorkflowDocument.ts
index fc0fcde..245a0f4 100644
--- a/server/gx-workflow-ls-format2/src/gxFormat2WorkflowDocument.ts
+++ b/server/gx-workflow-ls-format2/src/gxFormat2WorkflowDocument.ts
@@ -65,11 +65,13 @@ export class GxFormat2WorkflowDocument extends WorkflowDocument {
     const inputDocNode = this.nodeManager.getPropertyNodeByName(input, "doc");
     const inputDescription = String(inputDocNode?.valueNode?.value ?? "");
     const defaultValueNode = this.nodeManager.getPropertyNodeByName(input, "default");
+    const optionalValue = this.nodeManager.getPropertyValueByName(input, "optional");
     const inputDefinition: WorkflowInput = {
       name: inputName,
       doc: inputDescription,
       type: inputType,
       default: defaultValueNode?.valueNode?.value,
+      optional: optionalValue === undefined ? undefined : optionalValue === true,
     };
     return inputDefinition;
   }
diff --git a/server/gx-workflow-ls-format2/src/validation/rules/InputTypeValidationRule.ts b/server/gx-workflow-ls-format2/src/validation/rules/InputTypeValidationRule.ts
index ced1137..6798f63 100644
--- a/server/gx-workflow-ls-format2/src/validation/rules/InputTypeValidationRule.ts
+++ b/server/gx-workflow-ls-format2/src/validation/rules/InputTypeValidationRule.ts
@@ -18,7 +18,7 @@ export class InputTypeValidationRule implements ValidationRule {
       const inputName = String(input.keyNode.value);
       const inputTypeValue = documentContext.nodeManager.getPropertyValueByName(input, "type");
       const defaultValueNode = documentContext.nodeManager.getPropertyNodeByName(input, "default");
-      const defaultValue = defaultValueNode.valueNode?.value;
+      const defaultValue = defaultValueNode?.valueNode?.value;
 
       const defaultValueType = typeof defaultValue;
       if (inputTypeValue && defaultValue) {
diff --git a/server/gx-workflow-ls-format2/tests/integration/document.test.ts b/server/gx-workflow-ls-format2/tests/integration/document.test.ts
index 10cfe54..1e4440a 100644
--- a/server/gx-workflow-ls-format2/tests/integration/document.test.ts
+++ b/server/gx-workflow-ls-format2/tests/integration/document.test.ts
@@ -9,6 +9,7 @@ inputs:
   input_2:
     type: File
     doc: This is the input 2
+    optional: false
   the_collection:
     type: collection
     doc: This is a collection
@@ -34,6 +35,7 @@ inputs:
         name: "input_2",
         doc: "This is the input 2",
         type: "File",
+        optional: false,
       },
       {
         name: "the_collection",
@@ -50,6 +52,7 @@ inputs:
         doc: "",
         type: "text",
         default: "text value",
+        optional: true,
       },
     ]);
   });
diff --git a/server/gx-workflow-ls-native/src/nativeWorkflowDocument.ts b/server/gx-workflow-ls-native/src/nativeWorkflowDocument.ts
index fc0e4dc..83d5f75 100644
--- a/server/gx-workflow-ls-native/src/nativeWorkflowDocument.ts
+++ b/server/gx-workflow-ls-native/src/nativeWorkflowDocument.ts
@@ -70,6 +70,7 @@ export class NativeWorkflowDocument extends WorkflowDocument {
           doc: String(annotationValue ?? ""),
           type: this.getInputType(stepTypeValue, toolStateValue),
           default: toolStateValue.default,
+          optional: toolStateValue.optional,
         };
         result.inputs.push(inputDefinition);
       }
diff --git a/server/gx-workflow-ls-native/tests/unit/nativeWorkflowDocument.test.ts b/server/gx-workflow-ls-native/tests/unit/nativeWorkflowDocument.test.ts
index 7b0c29d..0ab3134 100644
--- a/server/gx-workflow-ls-native/tests/unit/nativeWorkflowDocument.test.ts
+++ b/server/gx-workflow-ls-native/tests/unit/nativeWorkflowDocument.test.ts
@@ -50,13 +50,13 @@ describe("NativeWorkflowDocument", () => {
       [
         TestWorkflowProvider.workflows.validation.withOnlyInputs,
         [
-          { default: undefined, doc: "", name: "Dataset Input", type: "data" },
-          { default: undefined, doc: "", name: "Collection Input", type: "collection" },
-          { default: undefined, doc: "", name: "Text Param", type: "text" },
-          { default: 10, doc: "", name: "Integer Param", type: "integer" },
-          { default: undefined, doc: "", name: "Float Param", type: "float" },
-          { default: undefined, doc: "", name: "Boolean Param", type: "boolean" },
-          { default: undefined, doc: "", name: "Color Param", type: "color" },
+          { default: undefined, doc: "", name: "Dataset Input", optional: false, type: "data" },
+          { default: undefined, doc: "", name: "Collection Input", optional: false, type: "collection" },
+          { default: undefined, doc: "", name: "Text Param", optional: false, type: "text" },
+          { default: 10, doc: "", name: "Integer Param", optional: true, type: "integer" },
+          { default: undefined, doc: "", name: "Float Param", optional: false, type: "float" },
+          { default: undefined, doc: "", name: "Boolean Param", optional: false, type: "boolean" },
+          { default: undefined, doc: "", name: "Color Param", optional: false, type: "color" },
         ],
       ],
     ])("returns the expected inputs", (wfContent: string, expectedInputs: WorkflowInput[]) => {
diff --git a/server/packages/server-common/src/ast/nodeManager.ts b/server/packages/server-common/src/ast/nodeManager.ts
index be157ea..90561a6 100644
--- a/server/packages/server-common/src/ast/nodeManager.ts
+++ b/server/packages/server-common/src/ast/nodeManager.ts
@@ -208,7 +208,7 @@ export class ASTNodeManager {
     }
   }
 
-  public getPropertyNodeByName(node: PropertyASTNode, propertyName: string): PropertyASTNode {
+  public getPropertyNodeByName(node: PropertyASTNode, propertyName: string): PropertyASTNode | undefined {
     const targetProperty = node.valueNode?.children?.find(
       (prop) => prop.type === "property" && prop.keyNode.value === propertyName
     ) as PropertyASTNode;
@@ -217,7 +217,7 @@ export class ASTNodeManager {
 
   public getPropertyValueByName(node: PropertyASTNode, propertyName: string): ValueTypes | undefined {
     const targetProperty = this.getPropertyNodeByName(node, propertyName);
-    const targetValue = targetProperty.valueNode?.value;
+    const targetValue = targetProperty?.valueNode?.value;
     return targetValue;
   }
 }
diff --git a/shared/src/requestsDefinitions.ts b/shared/src/requestsDefinitions.ts
index 48280fd..90bd7a3 100644
--- a/shared/src/requestsDefinitions.ts
+++ b/shared/src/requestsDefinitions.ts
@@ -48,6 +48,7 @@ export interface WorkflowInput {
   type: WorkflowDataType;
   doc: string;
   default?: unknown;
+  optional?: boolean;
 }
 
 export interface GetWorkflowInputsResult {