diff --git a/langchain-core/src/tools/index.ts b/langchain-core/src/tools/index.ts
index 3a73a0b53dde..a2000a24b21d 100644
--- a/langchain-core/src/tools/index.ts
+++ b/langchain-core/src/tools/index.ts
@@ -430,7 +430,7 @@ export class DynamicStructuredTool<
     this.func = fields.func;
     this.returnDirect = fields.returnDirect ?? this.returnDirect;
     this.schema = (
-      isZodSchema(fields.schema) ? fields.schema : z.object({})
+      isZodSchema(fields.schema) ? fields.schema : z.object({}).passthrough()
     ) as T extends ZodObjectAny ? T : ZodObjectAny;
   }
 
@@ -557,7 +557,11 @@ export function tool<
   | DynamicStructuredTool<T extends ZodObjectAny ? T : ZodObjectAny>
   | DynamicTool {
   // If the schema is not provided, or it's a string schema, create a DynamicTool
-  if (!fields.schema || !("shape" in fields.schema) || !fields.schema.shape) {
+  if (
+    !fields.schema ||
+    (isZodSchema(fields.schema) &&
+      (!("shape" in fields.schema) || !fields.schema.shape))
+  ) {
     return new DynamicTool({
       ...fields,
       description:
diff --git a/langchain-core/src/tools/tests/tools.test.ts b/langchain-core/src/tools/tests/tools.test.ts
index 4c38800b3489..2988eb64d9cf 100644
--- a/langchain-core/src/tools/tests/tools.test.ts
+++ b/langchain-core/src/tools/tests/tools.test.ts
@@ -128,7 +128,11 @@ test("Tool declared with JSON schema", async () => {
     required: ["location"],
   };
   const weatherTool = tool(
-    (_) => {
+    (input) => {
+      // even without validation expect input to be passed
+      expect(input).toEqual({
+        somethingSilly: true,
+      });
       return "Sunny";
     },
     {
@@ -136,15 +140,21 @@ test("Tool declared with JSON schema", async () => {
       schema: weatherSchema,
     }
   );
+  expect(weatherTool).toBeInstanceOf(DynamicStructuredTool);
 
   const weatherTool2 = new DynamicStructuredTool({
     name: "weather",
     description: "get the weather",
-    func: async (_) => {
+    func: async (input) => {
+      // even without validation expect input to be passed
+      expect(input).toEqual({
+        somethingSilly: true,
+      });
       return "Sunny";
     },
     schema: weatherSchema,
   });
+
   // No validation on JSON schema tools
   await weatherTool.invoke({
     somethingSilly: true,