diff --git a/src/tool/factory.test.ts b/src/tool/factory.test.ts
index fc47c98054..33c3a3bf0e 100644
--- a/src/tool/factory.test.ts
+++ b/src/tool/factory.test.ts
@@ -167,4 +167,80 @@ describe("tool factory", () => {
       assertStringIncludes(t.id, "tool_");
     });
   });
+
+  describe("dynamicTool input validation", () => {
+    it("should validate input with Zod schema", async () => {
+      const t = dynamicTool({
+        id: "zod-validate",
+        description: "desc",
+        inputSchema: z.object({ query: z.string() }),
+        execute: async (input) => input,
+      });
+      const result = await t.execute({ query: "test" });
+      assertEquals(result, { query: "test" });
+    });
+
+    it("should reject invalid input when Zod schema is provided", async () => {
+      const t = dynamicTool({
+        id: "zod-reject",
+        description: "desc",
+        inputSchema: z.object({ query: z.string() }),
+        execute: async () => "ok",
+      });
+      await assertRejects(
+        () => t.execute({ query: 123 }),
+        Error,
+      );
+    });
+
+    it("should accept valid object input without Zod schema", async () => {
+      const t = dynamicTool({
+        id: "no-schema-obj",
+        description: "desc",
+        inputSchema: {},
+        execute: async (input) => input,
+      });
+      const result = await t.execute({ foo: "bar" });
+      assertEquals(result, { foo: "bar" });
+    });
+
+    it("should reject null input without schema", async () => {
+      const t = dynamicTool({
+        id: "no-schema-null",
+        description: "desc",
+        inputSchema: {},
+        execute: async (input) => input,
+      });
+      await assertRejects(
+        () => t.execute(null),
+        Error,
+        "input must be a non-null object",
+      );
+    });
+
+    it("should coerce undefined input to empty object for zero-input tools", async () => {
+      const t = dynamicTool({
+        id: "no-schema-undef",
+        description: "desc",
+        inputSchema: {},
+        execute: async (input) => input,
+      });
+      const result = await t.execute(undefined);
+      assertEquals(result, {});
+    });
+
+    it("should reject primitive input without schema", async () => {
+      const t = dynamicTool({
+        id: "no-schema-prim",
+        description: "desc",
+        inputSchema: {},
+        execute: async (input) => input,
+      });
+      await assertRejects(
+        () => t.execute("string-input"),
+        Error,
+        "input must be a non-null object",
+      );
+    });
+  });
 });
diff --git a/src/tool/factory.ts b/src/tool/factory.ts
index 69d0d9e3fe..b6d3ed61af 100644
--- a/src/tool/factory.ts
+++ b/src/tool/factory.ts
@@ -186,6 +186,16 @@ export function dynamicTool(config: DynamicToolConfig): Tool<unknown, unknown> {
     inputSchema: config.inputSchema as z.ZodSchema<unknown>,
     inputSchemaJson,
     execute: async (input: unknown, context?: ToolExecutionContext) => {
+      if (
+        config.inputSchema &&
+        typeof (config.inputSchema as { parse?: unknown }).parse === "function"
+      ) {
+        (config.inputSchema as { parse: (v: unknown) => unknown }).parse(input);
+      } else if (input === undefined) {
+        input = {};
+      } else if (input === null || typeof input !== "object") {
+        throw new Error("dynamicTool: input must be a non-null object");
+      }
       const result = await config.execute(input, context);
       return config.toModelOutput ? config.toModelOutput(result) : result;
     },