diff --git a/teachertool/src/components/AskAIOverlay.tsx b/teachertool/src/components/AskAIOverlay.tsx
index 7e5504188b77..1b2a0dc811b5 100644
--- a/teachertool/src/components/AskAIOverlay.tsx
+++ b/teachertool/src/components/AskAIOverlay.tsx
@@ -8,7 +8,7 @@ import { FocusTrap } from "react-common/components/controls/FocusTrap";
 import { Accordion } from "react-common/components/controls/Accordion";
 import { classList } from "react-common/components/util";
 
-import { Strings } from "../constants";
+import { Constants, Strings } from "../constants";
 import { setAskAiOpen } from "../transforms/setAskAiOpen";
 import { addAiQuestionCriteriaToChecklist } from "../transforms/addAiQuestionCriteriaToChecklist";
 import { showToast } from "../transforms/showToast";
@@ -243,7 +243,11 @@ export const AskAIOverlay = () => {
                                         <Accordion.Panel>
                                             {customPrompts.length > 0 && (
                                                 <div className={css["custom-list"]}>
-                                                    {customPrompts.map((p, index) => (
+                                                    {customPrompts.map((p, index) => {
+                                                        const trimmedText = p.text.trim();
+                                                        const hasError = trimmedText && trimmedText.length < Constants.MinAIQuestionLength;
+
+                                                        return (
                                                         <div key={p.id} className={css["custom-item"]}>
                                                             <div className={css["custom-header"]}>
                                                                 <Checkbox
@@ -263,17 +267,30 @@ export const AskAIOverlay = () => {
                                                                     />
                                                                 )}
                                                             </div>
-                                                            <Textarea
-                                                                id={`ask-ai-custom-text-${p.id}`}
-                                                                className={css["textarea"]}
-                                                                placeholder={Strings.CustomPromptPlaceholder}
-                                                                initialValue={p.text}
-                                                                maxLength={aiQuestionMaxLength}
-                                                                showRemainingCharacterCount={100}
-                                                                onChange={text => setCustomTextForId(p.id, text)}
-                                                            />
+                                                            <div
+                                                                className={classList(css["custom-textarea-wrapper"], hasError ? css["textarea-error"] : undefined)}
+                                                                title={hasError ? Strings.QuestionTooShort : undefined}
+                                                            >
+                                                                <Textarea
+                                                                    id={`ask-ai-custom-text-${p.id}`}
+                                                                    className={css["textarea"]}
+                                                                    placeholder={Strings.CustomPromptPlaceholder}
+                                                                    initialValue={p.text}
+                                                                    maxLength={aiQuestionMaxLength}
+                                                                    showRemainingCharacterCount={100}
+                                                                    resize="vertical"
+                                                                    title={hasError ? Strings.QuestionTooShort : undefined}
+                                                                    onChange={text => setCustomTextForId(p.id, text)}
+                                                                />
+                                                                {hasError && (
+                                                                    <i
+                                                                        className={classList(css["validation-icon"], "fas", "fa-exclamation-triangle")}
+                                                                        aria-hidden="true"
+                                                                    />
+                                                                )}
+                                                            </div>
                                                         </div>
-                                                    ))}
+                                                    )})}
                                                 </div>
                                             )}
 
diff --git a/teachertool/src/components/CriteriaInstanceDisplay.tsx b/teachertool/src/components/CriteriaInstanceDisplay.tsx
index ac0c8d746bcf..f6e2f7857298 100644
--- a/teachertool/src/components/CriteriaInstanceDisplay.tsx
+++ b/teachertool/src/components/CriteriaInstanceDisplay.tsx
@@ -9,7 +9,7 @@ import { useContext, useEffect, useMemo, useState } from "react";
 import { Input } from "react-common/components/controls/Input";
 import { Button } from "react-common/components/controls/Button";
 import { AppStateContext } from "../state/appStateContext";
-import { Strings, Ticks } from "../constants";
+import { Constants, Strings, Ticks } from "../constants";
 import { showModal } from "../transforms/showModal";
 import { BlockPickerOptions } from "../types/modalOptions";
 import { validateParameterValue } from "../utils/validateParameterValue";
@@ -21,6 +21,7 @@ interface InlineInputSegmentProps {
     param: CriteriaParameterValue;
     shouldExpand: boolean;
     numeric: boolean;
+    minLength?: number;
 }
 const InlineInputSegment: React.FC<InlineInputSegmentProps> = ({
     initialValue,
@@ -28,6 +29,7 @@ const InlineInputSegment: React.FC<InlineInputSegmentProps> = ({
     param,
     shouldExpand,
     numeric,
+    minLength,
 }) => {
     const [errorMessage, setErrorMessage] = useState(initialValue ? "" : Strings.ValueRequired);
     const paramDefinition = useMemo(() => getParameterDefinition(instance.catalogCriteriaId, param.name), [param]);
@@ -58,6 +60,11 @@ const InlineInputSegment: React.FC<InlineInputSegmentProps> = ({
             return;
         }
 
+        if (minLength && initialValue.trim().length < minLength) {
+            setErrorMessage(Strings.QuestionTooShort);
+            return;
+        }
+
         // We still allow some invalid values to be set on the parameter so the user can see what they typed
         // and the associated error.
         // Without this, we risk erroring too soon (i.e. typing in first digit of number with min > 10),
@@ -76,6 +83,10 @@ const InlineInputSegment: React.FC<InlineInputSegmentProps> = ({
             setErrorMessage(Strings.ValueRequired);
         }
 
+        if (minLength && newValue.trim().length < minLength) {
+            setErrorMessage(Strings.QuestionTooShort);
+        }
+
         setParameterValue(instance.instanceId, param.name, newValue);
     }
 
@@ -234,6 +245,10 @@ export const CriteriaInstanceDisplay: React.FC<CriteriaInstanceDisplayProps> = (
         if (paramDef.type === "block") {
             return <BlockInputSegment param={paramInstance} instance={criteriaInstance} />;
         } else {
+            const minLength =
+                catalogCriteria?.use === "ai_question" && paramDef.name === "question"
+                    ? Constants.MinAIQuestionLength
+                    : undefined;
             return (
                 <InlineInputSegment
                     initialValue={paramInstance.value}
@@ -241,6 +256,7 @@ export const CriteriaInstanceDisplay: React.FC<CriteriaInstanceDisplayProps> = (
                     instance={criteriaInstance}
                     shouldExpand={paramDef.type === "longString"}
                     numeric={paramDef.type === "number"}
+                    minLength={minLength}
                 />
             );
         }
diff --git a/teachertool/src/components/styling/AskAIOverlay.module.scss b/teachertool/src/components/styling/AskAIOverlay.module.scss
index 6f95f5fff20c..ba34935f3be0 100644
--- a/teachertool/src/components/styling/AskAIOverlay.module.scss
+++ b/teachertool/src/components/styling/AskAIOverlay.module.scss
@@ -156,6 +156,40 @@
 
     textarea[class*="common-textarea"] {
         min-height: 6rem;
+        resize: vertical;
+    }
+
+    .custom-textarea-wrapper {
+        position: relative;
+        &.textarea-error {
+            :global(.common-textarea-group) {
+                border: solid 1px var(--pxt-colors-red-background);
+                background-color: var(--pxt-colors-red-alpha10);
+                transition: background-color 0.3s ease-in-out, border 0.3s ease-in-out;
+
+                &:focus::after,
+                &:focus-within::after {
+                    border: solid 2px var(--pxt-colors-red-background);
+                }
+            }
+
+            textarea[class*="common-textarea"] {
+                padding-right: 2rem;
+            }
+
+            .validation-icon {
+                color: var(--pxt-colors-red-background) !important;
+            }
+        }
+    }
+
+    .validation-icon {
+        position: absolute;
+        top: 0.7rem;
+        right: 0.75rem;
+        font-size: 0.9rem;
+        pointer-events: none;
+        color: var(--pxt-colors-red-background);
     }
 }
 
diff --git a/teachertool/src/constants.ts b/teachertool/src/constants.ts
index d49cd2b74693..6000e8e830f7 100644
--- a/teachertool/src/constants.ts
+++ b/teachertool/src/constants.ts
@@ -1,3 +1,9 @@
+namespace Misc {
+    export const LearnMoreLink = "https://makecode.microbit.org/teachertool"; // TODO: Replace with golink or aka.ms link
+    export const ExperienceId = "code-eval";
+    export const MinAIQuestionLength = 10;
+}
+
 export namespace Strings {
     export const AppTitle = lf("Code Evaluation");
     export const AppTitleShort = lf("Code Eval");
@@ -18,7 +24,7 @@ export namespace Strings {
     export const AddCriteria = lf("Add Criteria");
     export const AskAI = lf("Ask AI");
     export const Custom = lf("Custom");
-    export const CustomPromptPlaceholder = lf("Write your own question here...");
+    export const CustomPromptPlaceholder = lf("Write your own question here (minimum {0} characters)...", Misc.MinAIQuestionLength);
     export const Actions = lf("Actions");
     export const RunOnLoad = lf("Evaluate on load");
     export const RunOnLoadDescription = lf("Automatically evaluate a project when it is loaded");
@@ -52,6 +58,7 @@ export namespace Strings {
     export const UnableToReachAI = lf("Unable to reach the AI service");
     export const UnexpectedError = lf("An unexpected error occurred");
     export const Dismiss = lf("Dismiss");
+    export const QuestionTooShort = lf("Question must be at least {0} characters", Misc.MinAIQuestionLength);
     export const EvaluationComplete = lf("Evaluation complete");
     export const UnableToEvaluatePartial = lf("Unable to evaluate some criteria");
     export const GiveFeedback = lf("Give Feedback");
@@ -104,9 +111,4 @@ export namespace Ticks {
     export const TermsOfUseClicked = "teachertool.termsofuse.clicked";
 }
 
-namespace Misc {
-    export const LearnMoreLink = "https://makecode.microbit.org/teachertool"; // TODO: Replace with golink or aka.ms link
-    export const ExperienceId = "code-eval";
-}
-
 export const Constants = Object.assign(Misc, { Strings, Ticks });