diff --git a/public/scripts/extensions/expressions/index.js b/public/scripts/extensions/expressions/index.js
index da527dd8b..c70eeaef0 100644
--- a/public/scripts/extensions/expressions/index.js
+++ b/public/scripts/extensions/expressions/index.js
@@ -1,14 +1,15 @@
-import { callPopup, eventSource, event_types, generateQuietPrompt, getRequestHeaders, saveSettingsDebounced, substituteParams } from '../../../script.js';
+import { callPopup, eventSource, event_types, generateQuietPrompt, getRequestHeaders, online_status, saveSettingsDebounced, substituteParams } from '../../../script.js';
 import { dragElement, isMobile } from '../../RossAscends-mods.js';
 import { getContext, getApiUrl, modules, extension_settings, ModuleWorkerWrapper, doExtrasFetch, renderExtensionTemplateAsync } from '../../extensions.js';
 import { loadMovingUIState, power_user } from '../../power-user.js';
-import { onlyUnique, debounce, getCharaFilename, trimToEndSentence, trimToStartSentence } from '../../utils.js';
+import { onlyUnique, debounce, getCharaFilename, trimToEndSentence, trimToStartSentence, waitUntilCondition } from '../../utils.js';
 import { hideMutedSprites } from '../../group-chats.js';
 import { isJsonSchemaSupported } from '../../textgen-settings.js';
 import { debounce_timeout } from '../../constants.js';
 import { SlashCommandParser } from '../../slash-commands/SlashCommandParser.js';
 import { SlashCommand } from '../../slash-commands/SlashCommand.js';
 import { ARGUMENT_TYPE, SlashCommandArgument } from '../../slash-commands/SlashCommandArgument.js';
+import { isFunctionCallingSupported } from '../../openai.js';
 export { MODULE_NAME };
 
 const MODULE_NAME = 'expressions';
@@ -16,6 +17,7 @@ const UPDATE_INTERVAL = 2000;
 const STREAMING_UPDATE_INTERVAL = 10000;
 const TALKINGCHECK_UPDATE_INTERVAL = 500;
 const DEFAULT_FALLBACK_EXPRESSION = 'joy';
+const FUNCTION_NAME = 'set_emotion';
 const DEFAULT_LLM_PROMPT = 'Pause your roleplay. Classify the emotion of the last message. Output just one word, e.g. "joy" or "anger". Choose only one of the following labels: {{labels}}';
 const DEFAULT_EXPRESSIONS = [
     'talkinghead',
@@ -1001,6 +1003,10 @@ async function getLlmPrompt(labels) {
         return '';
     }
 
+    if (isFunctionCallingSupported()) {
+        return '';
+    }
+
     const labelsString = labels.map(x => `"${x}"`).join(', ');
     const prompt = substituteParams(String(extension_settings.expressions.llmPrompt))
         .replace(/{{labels}}/gi, labelsString);
@@ -1018,7 +1024,13 @@ function parseLlmResponse(emotionResponse, labels) {
 
     try {
         const parsedEmotion = JSON.parse(emotionResponse);
-        return parsedEmotion?.emotion ?? fallbackExpression;
+        const response = parsedEmotion?.emotion;
+
+        if (!response || !labels.includes(response)) {
+            return fallbackExpression;
+        }
+
+        return response;
     } catch {
         const fuse = new Fuse(labels, { includeScore: true });
         console.debug('Using fuzzy search in labels:', labels);
@@ -1032,6 +1044,40 @@ function parseLlmResponse(emotionResponse, labels) {
     throw new Error('Could not parse emotion response ' + emotionResponse);
 }
 
+/**
+ * Registers the function tool for the LLM API.
+ * @param {FunctionToolRegister} args Function tool register arguments.
+ */
+function onFunctionToolRegister(args) {
+    if (inApiCall && extension_settings.expressions.api === EXPRESSION_API.llm && isFunctionCallingSupported()) {
+        // Only trigger on quiet mode
+        if (args.type !== 'quiet') {
+            return;
+        }
+
+        const emotions = DEFAULT_EXPRESSIONS.filter((e) => e != 'talkinghead');
+        const jsonSchema = {
+            $schema: 'http://json-schema.org/draft-04/schema#',
+            type: 'object',
+            properties: {
+                emotion: {
+                    type: 'string',
+                    enum: emotions,
+                },
+            },
+            required: [
+                'emotion',
+            ],
+        };
+        args.registerFunctionTool(
+            FUNCTION_NAME,
+            substituteParams('Sets the label that best describes the current emotional state of {{char}}. Only select one of the enumerated values.'),
+            jsonSchema,
+            true,
+        );
+    }
+}
+
 function onTextGenSettingsReady(args) {
     // Only call if inside an API call
     if (inApiCall && extension_settings.expressions.api === EXPRESSION_API.llm && isJsonSchemaSupported()) {
@@ -1087,11 +1133,27 @@ async function getExpressionLabel(text) {
             } break;
             // Using LLM
             case EXPRESSION_API.llm: {
+                try {
+                    await waitUntilCondition(() => online_status !== 'no_connection', 3000, 250);
+                } catch (error) {
+                    console.warn('No LLM connection. Using fallback expression', error);
+                    return getFallbackExpression();
+                }
+
                 const expressionsList = await getExpressionsList();
                 const prompt = await getLlmPrompt(expressionsList);
+                let functionResult = null;
                 eventSource.once(event_types.TEXT_COMPLETION_SETTINGS_READY, onTextGenSettingsReady);
+                eventSource.once(event_types.LLM_FUNCTION_TOOL_REGISTER, onFunctionToolRegister);
+                eventSource.once(event_types.LLM_FUNCTION_TOOL_CALL, (/** @type {FunctionToolCall} */ args) => {
+                    if (args.name !== FUNCTION_NAME) {
+                        return;
+                    }
+
+                    functionResult = args?.arguments;
+                });
                 const emotionResponse = await generateQuietPrompt(prompt, false, false);
-                return parseLlmResponse(emotionResponse, expressionsList);
+                return parseLlmResponse(functionResult || emotionResponse, expressionsList);
             }
             // Extras
             default: {
diff --git a/public/scripts/extensions/expressions/settings.html b/public/scripts/extensions/expressions/settings.html
index abb0219ce..e819d3bfd 100644
--- a/public/scripts/extensions/expressions/settings.html
+++ b/public/scripts/extensions/expressions/settings.html
@@ -34,7 +34,7 @@
                         <i class="fa-solid fa-clock-rotate-left fa-sm"></i>
                     </div>
                 </label>
-                <small>Will be used if the API doesn't support JSON schemas.</small>
+                <small>Will be used if the API doesn't support JSON schemas or function calling.</small>
                 <textarea id="expression_llm_prompt" type="text" class="text_pole textarea_compact" rows="2" placeholder="Use &lcub;&lcub;labels&rcub;&rcub; special macro."></textarea>
             </div>
             <div class="expression_fallback_block m-b-1 m-t-1">