diff --git a/.changeset/khaki-plums-mate.md b/.changeset/khaki-plums-mate.md
new file mode 100644
index 0000000..e2a525f
--- /dev/null
+++ b/.changeset/khaki-plums-mate.md
@@ -0,0 +1,5 @@
+---
+"@plotday/twister": minor
+---
+
+Added: Options tool for defining user-configurable options for twists
diff --git a/twister/package.json b/twister/package.json
index 2e1816d..91445ac 100644
--- a/twister/package.json
+++ b/twister/package.json
@@ -35,6 +35,11 @@
       "types": "./dist/tag.d.ts",
       "default": "./dist/tag.js"
     },
+    "./options": {
+      "@plotday/source": "./src/options.ts",
+      "types": "./dist/options.d.ts",
+      "default": "./dist/options.js"
+    },
     "./tools/twists": {
       "@plotday/source": "./src/tools/twists.ts",
       "types": "./dist/tools/twists.d.ts",
diff --git a/twister/src/index.ts b/twister/src/index.ts
index 0a5d181..a0bc135 100644
--- a/twister/src/index.ts
+++ b/twister/src/index.ts
@@ -3,5 +3,6 @@ export * from "./plot";
 export * from "./tag";
 export * from "./tool";
 export * from "./tools";
+export * from "./options";
 export * from "./utils/types";
 export { getBuilderDocumentation } from "./creator-docs";
diff --git a/twister/src/options.ts b/twister/src/options.ts
new file mode 100644
index 0000000..6d23c04
--- /dev/null
+++ b/twister/src/options.ts
@@ -0,0 +1,112 @@
+import { ITool } from "./tool";
+
+/**
+ * A select option definition for twist configuration.
+ * Renders as a dropdown in the Flutter UI.
+ */
+export type SelectDef = {
+  type: "select";
+  label: string;
+  description?: string;
+  choices: ReadonlyArray<{ value: string; label: string }>;
+  default: string;
+};
+
+/**
+ * A text input option definition for twist configuration.
+ * Renders as a text field in the Flutter UI.
+ */
+export type TextDef = {
+  type: "text";
+  label: string;
+  description?: string;
+  default: string;
+  placeholder?: string;
+};
+
+/**
+ * A number input option definition for twist configuration.
+ * Renders as a number field in the Flutter UI.
+ */
+export type NumberDef = {
+  type: "number";
+  label: string;
+  description?: string;
+  default: number;
+  min?: number;
+  max?: number;
+};
+
+/**
+ * A boolean toggle option definition for twist configuration.
+ * Renders as a switch in the Flutter UI.
+ */
+export type BooleanDef = {
+  type: "boolean";
+  label: string;
+  description?: string;
+  default: boolean;
+};
+
+/**
+ * Union of all option definition types.
+ */
+export type OptionDef = SelectDef | TextDef | NumberDef | BooleanDef;
+
+/**
+ * Schema defining all configurable options for a twist.
+ * Each key maps to an option definition that describes its type, label, and default value.
+ */
+export type OptionsSchema = Record<string, OptionDef>;
+
+/**
+ * Infers the resolved value types from an options schema.
+ * Boolean options resolve to `boolean`, number options to `number`,
+ * and select/text options to `string`.
+ */
+export type ResolvedOptions<T extends OptionsSchema> = {
+  [K in keyof T]: T[K] extends BooleanDef
+    ? boolean
+    : T[K] extends NumberDef
+      ? number
+      : string;
+};
+
+/**
+ * Built-in marker class for twist configuration options.
+ *
+ * Declare options in your twist's `build()` method to expose configurable
+ * settings to users. The schema is introspected at deploy time and stored
+ * alongside permissions. At runtime, user values are merged with defaults.
+ *
+ * @example
+ * ```typescript
+ * import { Options, type OptionsSchema } from "@plotday/twister/options";
+ *
+ * export default class MyTwist extends Twist<MyTwist> {
+ *   build(build: ToolBuilder) {
+ *     return {
+ *       options: build(Options, {
+ *         model: {
+ *           type: 'select',
+ *           label: 'AI Model',
+ *           choices: [
+ *             { value: 'fast', label: 'Fast' },
+ *             { value: 'smart', label: 'Smart' },
+ *           ],
+ *           default: 'fast',
+ *         },
+ *       }),
+ *       // ... other tools
+ *     };
+ *   }
+ *
+ *   async respond(note: Note) {
+ *     const model = this.tools.options.model; // typed as string
+ *   }
+ * }
+ * ```
+ */
+export abstract class Options extends ITool {
+  static readonly toolId = "Options";
+}
diff --git a/twister/src/utils/types.ts b/twister/src/utils/types.ts
index 52b8fcd..369624e 100644
--- a/twister/src/utils/types.ts
+++ b/twister/src/utils/types.ts
@@ -8,6 +8,7 @@
  *
  * @internal
  */
+import type { Options, OptionsSchema, ResolvedOptions } from "../options";
 import type { Callbacks } from "../tools/callbacks";
 import type { Store } from "../tools/store";
 import type { Tasks } from "../tools/tasks";
@@ -63,10 +64,16 @@ export type InferOptions<T> = T extends {
  * Function type for building tool dependencies.
  * Used in build methods to request tool instances.
  */
-export type ToolBuilder = <TC extends abstract new (...args: any) => any>(
-  ToolClass: TC,
-  options?: InferOptions<TC>
-) => Promise<InstanceType<TC>>;
+export type ToolBuilder = {
+  <T extends OptionsSchema>(
+    ToolClass: typeof Options,
+    schema: T
+  ): Promise<ResolvedOptions<T>>;
+  <TC extends abstract new (...args: any) => any>(
+    ToolClass: TC,
+    options?: InferOptions<TC>
+  ): Promise<InstanceType<TC>>;
+};
 
 /**
  * Interface for managing tool initialization and lifecycle.
diff --git a/twists/chat/src/index.ts b/twists/chat/src/index.ts
index 7e8b308..d455761 100644
--- a/twists/chat/src/index.ts
+++ b/twists/chat/src/index.ts
@@ -9,12 +9,28 @@ import {
   type ToolBuilder,
   Twist,
 } from "@plotday/twister";
-import { AI, type AIMessage } from "@plotday/twister/tools/ai";
+import { Options } from "@plotday/twister/options";
+import { AI, type AIMessage, AIModel } from "@plotday/twister/tools/ai";
 import { ActivityAccess, Plot } from "@plotday/twister/tools/plot";
 
 export default class ChatTwist extends Twist<ChatTwist> {
   build(build: ToolBuilder) {
     return {
+      options: build(Options, {
+        model: {
+          type: "select" as const,
+          label: "AI Model",
+          description: "The AI model used for chat responses",
+          choices: [
+            { value: "anthropic/claude-sonnet-4-5", label: "Claude Sonnet 4.5" },
+            { value: "anthropic/claude-haiku-4-5", label: "Claude Haiku 4.5 (Fast)" },
+            { value: "openai/gpt-5", label: "GPT-5" },
+            { value: "google/gemini-2.5-pro", label: "Gemini 2.5 Pro" },
+            { value: "google/gemini-2.5-flash", label: "Gemini 2.5 Flash (Fast)" },
+          ],
+          default: "anthropic/claude-sonnet-4-5",
+        },
+      }),
       ai: build(AI),
       plot: build(Plot, {
         activity: {
@@ -111,7 +127,7 @@ You can provide either or both inline and standalone links. Only use standalone
     });
 
     const response = await this.tools.ai.prompt({
-      model: { speed: "balanced", cost: "medium" },
+      model: { speed: "balanced", cost: "medium", hint: this.tools.options.model as AIModel },
       messages,
       outputSchema: schema,
     });