diff --git a/src/app/(dashboard)/dashboard/playground/hooks/useStructuredOutput.ts b/src/app/(dashboard)/dashboard/playground/hooks/useStructuredOutput.ts
new file mode 100644
index 0000000000..7eb621600a
--- /dev/null
+++ b/src/app/(dashboard)/dashboard/playground/hooks/useStructuredOutput.ts
@@ -0,0 +1,124 @@
+// src/app/(dashboard)/dashboard/playground/hooks/useStructuredOutput.ts
+"use client";
+
+import { useState, useCallback } from "react";
+import { StructuredOutputSchema } from "@/shared/schemas/playground";
+
+export interface StructuredOutputSchemaInput {
+  name: string;
+  schema: Record<string, unknown>;
+  strict?: boolean;
+}
+
+export interface UseStructuredOutputState {
+  enabled: boolean;
+  schema: StructuredOutputSchemaInput | null;
+  error: string | null;
+}
+
+export interface ValidateResponseResult {
+  valid: boolean;
+  error?: string;
+}
+
+export interface UseStructuredOutput extends UseStructuredOutputState {
+  setEnabled: (enabled: boolean) => void;
+  /**
+   * Set and validate the JSON schema via Zod StructuredOutputSchema.
+   * Clears error on success; sets error on validation failure.
+   */
+  setSchema: (s: StructuredOutputSchemaInput) => void;
+  /**
+   * Validate a response body against the current schema.
+   * - First tries JSON.parse if content is a string.
+   * - Then checks that the parsed value is a non-null object (basic shape validation).
+   * Returns { valid: true } on success; { valid: false, error } on failure.
+   */
+  validateResponse: (content: unknown) => ValidateResponseResult;
+}
+
+/**
+ * Hook for the Structured Output (JSON mode) toggle in the Build tab.
+ * Manages toggle state + JSON schema + client-side response validation.
+ */
+export function useStructuredOutput(): UseStructuredOutput {
+  const [enabled, setEnabledState] = useState(false);
+  const [schema, setSchemaState] = useState<StructuredOutputSchemaInput | null>(null);
+  const [error, setError] = useState<string | null>(null);
+
+  const setEnabled = useCallback((value: boolean): void => {
+    setEnabledState(value);
+  }, []);
+
+  const setSchema = useCallback((s: StructuredOutputSchemaInput): void => {
+    // Validate via StructuredOutputSchema (wraps the input as if it were a full response_format object).
+    const parsed = StructuredOutputSchema.safeParse({
+      type: "json_schema",
+      json_schema: s,
+    });
+    if (!parsed.success) {
+      const message = parsed.error.issues.map((i) => i.message).join("; ");
+      setError(message);
+      return;
+    }
+    setSchemaState(s);
+    setError(null);
+  }, []);
+
+  const validateResponse = useCallback(
+    (content: unknown): ValidateResponseResult => {
+      if (schema == null) {
+        return { valid: false, error: "No schema set" };
+      }
+
+      // Step 1: parse JSON if the content is a string.
+      let parsed: unknown = content;
+      if (typeof content === "string") {
+        try {
+          parsed = JSON.parse(content);
+        } catch {
+          return { valid: false, error: "Response is not valid JSON" };
+        }
+      }
+
+      // Step 2: basic shape validation — must be a non-null object.
+      // Full JSON Schema validation would require ajv (not present in this project).
+      // We do a structural check: verify it's an object, and for each key in the
+      // schema's `properties` (if present), check that the key exists in the response.
+      if (parsed == null || typeof parsed !== "object" || Array.isArray(parsed)) {
+        return { valid: false, error: "Response is not a JSON object" };
+      }
+
+      const responseObj = parsed as Record<string, unknown>;
+      const schemaObj = schema.schema;
+
+      // If the schema has a "properties" field, validate that required keys are present.
+      const properties = schemaObj["properties"];
+      if (properties != null && typeof properties === "object" && !Array.isArray(properties)) {
+        const required = schemaObj["required"];
+        if (Array.isArray(required)) {
+          for (const key of required) {
+            if (typeof key === "string" && !(key in responseObj)) {
+              return {
+                valid: false,
+                error: `Response is missing required field: "${key}"`,
+              };
+            }
+          }
+        }
+      }
+
+      return { valid: true };
+    },
+    [schema],
+  );
+
+  return {
+    enabled,
+    schema,
+    error,
+    setEnabled,
+    setSchema,
+    validateResponse,
+  };
+}
diff --git a/src/app/(dashboard)/dashboard/playground/hooks/useToolsBuilder.ts b/src/app/(dashboard)/dashboard/playground/hooks/useToolsBuilder.ts
new file mode 100644
index 0000000000..a41950a3bf
--- /dev/null
+++ b/src/app/(dashboard)/dashboard/playground/hooks/useToolsBuilder.ts
@@ -0,0 +1,119 @@
+// src/app/(dashboard)/dashboard/playground/hooks/useToolsBuilder.ts
+"use client";
+
+import { useState, useCallback } from "react";
+import { ToolDefinitionSchema } from "@/shared/schemas/playground";
+import type { ToolDefinition } from "@/lib/playground/codeExport";
+
+export interface ToolsBuildResult {
+  ok: true;
+}
+
+export interface ToolsBuildError {
+  ok: false;
+  error: string;
+}
+
+export type ToolsBuildOutcome = ToolsBuildResult | ToolsBuildError;
+
+export interface UseToolsBuilderState {
+  tools: ToolDefinition[];
+  errors: Map<number, string>;
+}
+
+export interface UseToolsBuilder extends UseToolsBuilderState {
+  /**
+   * Add a tool after Zod validation.
+   * Returns { ok: true } on success; { ok: false, error } if validation fails.
+   */
+  add: (tool: ToolDefinition) => ToolsBuildOutcome;
+  /** Remove tool at given index. No-op if index out of bounds. */
+  remove: (index: number) => void;
+  /**
+   * Replace tool at index after Zod validation.
+   * Returns { ok: true } on success; { ok: false, error } if validation fails.
+   * Clears previous error for that index on success.
+   */
+  update: (index: number, tool: ToolDefinition) => ToolsBuildOutcome;
+  /** Remove all tools and clear all errors. */
+  clear: () => void;
+}
+
+/**
+ * Client-side manager for the `tools[]` array (Function Calling / Build tab).
+ *
+ * Validates each tool via Zod `ToolDefinitionSchema` before adding/updating.
+ * Stores per-index validation errors so the UI can show inline hints.
+ */
+export function useToolsBuilder(): UseToolsBuilder {
+  const [tools, setTools] = useState<ToolDefinition[]>([]);
+  const [errors, setErrors] = useState<Map<number, string>>(new Map());
+
+  const add = useCallback((tool: ToolDefinition): ToolsBuildOutcome => {
+    const parsed = ToolDefinitionSchema.safeParse(tool);
+    if (!parsed.success) {
+      const message = parsed.error.issues.map((i) => i.message).join("; ");
+      return { ok: false, error: message };
+    }
+    setTools((prev) => [...prev, parsed.data as ToolDefinition]);
+    return { ok: true };
+  }, []);
+
+  const remove = useCallback((index: number): void => {
+    setTools((prev) => {
+      if (index < 0 || index >= prev.length) return prev;
+      const next = [...prev];
+      next.splice(index, 1);
+      return next;
+    });
+    setErrors((prev) => {
+      const next = new Map(prev);
+      next.delete(index);
+      // Re-index errors for items after the removed one.
+      const reindexed = new Map<number, string>();
+      next.forEach((v, k) => {
+        reindexed.set(k > index ? k - 1 : k, v);
+      });
+      return reindexed;
+    });
+  }, []);
+
+  const update = useCallback((index: number, tool: ToolDefinition): ToolsBuildOutcome => {
+    const parsed = ToolDefinitionSchema.safeParse(tool);
+    if (!parsed.success) {
+      const message = parsed.error.issues.map((i) => i.message).join("; ");
+      setErrors((prev) => {
+        const next = new Map(prev);
+        next.set(index, message);
+        return next;
+      });
+      return { ok: false, error: message };
+    }
+    setTools((prev) => {
+      if (index < 0 || index >= prev.length) return prev;
+      const next = [...prev];
+      next[index] = parsed.data as ToolDefinition;
+      return next;
+    });
+    setErrors((prev) => {
+      const next = new Map(prev);
+      next.delete(index);
+      return next;
+    });
+    return { ok: true };
+  }, []);
+
+  const clear = useCallback((): void => {
+    setTools([]);
+    setErrors(new Map());
+  }, []);
+
+  return {
+    tools,
+    errors,
+    add,
+    remove,
+    update,
+    clear,
+  };
+}