diff --git a/server-node/src/routes/api/workflow-controller.ts b/server-node/src/routes/api/workflow-controller.ts
index b790944bc..a84e42f20 100644
--- a/server-node/src/routes/api/workflow-controller.ts
+++ b/server-node/src/routes/api/workflow-controller.ts
@@ -20,8 +20,17 @@ router.post("/:workflowUuid?", [
             return;
         }
  
-        // TODO: Validate input further (json may be invalid or not be in workflow format)
-        const workflow = JSON.parse(req.body.workflow);
+        try {
+            var workflow = JSON.parse(req.body.workflow);
+        } catch (err) {
+            if (err instanceof Error) {
+                console.error("malformed workflow-json was provided", err.message);
+                res.status(400).json({error: "Malformed workflow-JSON was provided. See Server-Logs for more info", details: err.message});
+                return;
+            } else {
+                throw err;
+            }
+        }
 
         // TODO: Replace with static multer function of pdffile
         const inputs = await Promise.all((req.files as Express.Multer.File[]).map(async file => {
@@ -32,12 +41,17 @@ router.post("/:workflowUuid?", [
         if(req.body.async === "false") {
             console.log("Don't do async");
 
-            let pdfResults = await traverseOperations(workflow.operations, inputs, (state) => {
+            traverseOperations(workflow.operations, inputs, (state) => {
                 console.log("State: ", state);
+            }).then(async (pdfResults) => {
+                console.log("Download");
+                await respondWithPdfFiles(res, pdfResults, "workflow-results");
+            }).catch((err) => {
+                if(err.validationError)
+                    res.status(400).json({error: err});
+                else
+                    throw err;
             })
-
-            console.log("Download");
-            await respondWithPdfFiles(res, pdfResults, "workflow-results");
         }
         else {
             console.log("Start Aync Workflow");
@@ -63,6 +77,7 @@ router.post("/:workflowUuid?", [
                 }
             });
 
+            // TODO: Handle when this throws errors
             let pdfResults = await traverseOperations(workflow.operations, inputs, (state) => {
                 console.log("State: ", state);
                 if(activeWorkflow.eventStream)
diff --git a/shared-operations/src/workflow/traverseOperations.ts b/shared-operations/src/workflow/traverseOperations.ts
index 4c459d2e5..fbf1bf139 100644
--- a/shared-operations/src/workflow/traverseOperations.ts
+++ b/shared-operations/src/workflow/traverseOperations.ts
@@ -6,11 +6,11 @@ import { validateOperations } from "./validateOperations";
 import { getOperatorByName } from "./getOperatorByName";
 
 export async function traverseOperations(operations: Action[], input: PdfFile[], progressCallback: (state: Progress) => void): Promise<PdfFile[]> {
-    
-    const validationResult = validateOperations(operations)
+    const validationResult = validateOperations(operations);
     if(!validationResult.valid) {
-        throw Error(validationResult.reason);
+        return Promise.reject({validationError: validationResult.reason});
     }
+    
     const waitOperations = organizeWaitOperations(operations);
 
     let results: PdfFile[] = [];
diff --git a/shared-operations/src/workflow/validateOperations.ts b/shared-operations/src/workflow/validateOperations.ts
index 2d3bd2f6f..653d41b85 100644
--- a/shared-operations/src/workflow/validateOperations.ts
+++ b/shared-operations/src/workflow/validateOperations.ts
@@ -1,16 +1,35 @@
 import { Action } from "../../declarations/Action";
+import { getOperatorByName } from "./getOperatorByName";
 
 export function validateOperations(actions: Action[]): { valid: boolean, reason?: string} {
-    // TODO: Validate using inbuilt validators: 
-    /*
-        validationResult = impose.validate()
-        if(validationResult.valid) {
-            // Check Next
-        }
-        else {
-            return validationResult.reason
-        }
-    */
+    function validateOperation(actions: Action[]): { valid: boolean; reason?: string; } {
+        for (const action of actions) {
+            if (action.type === "wait" || action.type === "done") {
+                // TODO: Validate these too ):
+                return { valid: true };
+            }
+            else {
+                const operator = getOperatorByName(action.type);
+                if(!operator) {
+                    return { valid: false, reason: `action.type ${action.type} does not exist` }
+                }
+                const validationResult = new operator(action).validate();
+    
+                if(!validationResult.valid) {
+                    return validationResult;
+                }
+            }
 
-    return { valid: true };
+            if (action.actions) {
+                const validationResult = validateOperation(action.actions);
+
+                if(!validationResult.valid) {
+                    return validationResult;
+                }
+            }
+        }
+        return { valid: true };
+    }
+
+    return validateOperation(actions);
 }
\ No newline at end of file