diff --git a/.changeset/lucky-candles-reply.md b/.changeset/lucky-candles-reply.md
new file mode 100644
index 000000000..01db7fd83
--- /dev/null
+++ b/.changeset/lucky-candles-reply.md
@@ -0,0 +1,5 @@
+---
+"deepagents": patch
+---
+
+fix: add default value to grep tool glob schema for strict mode compatibility
diff --git a/libs/deepagents/src/middleware/fs.test.ts b/libs/deepagents/src/middleware/fs.test.ts
index a23ab0a71..3f8af8b4b 100644
--- a/libs/deepagents/src/middleware/fs.test.ts
+++ b/libs/deepagents/src/middleware/fs.test.ts
@@ -817,6 +817,25 @@ describe("createFilesystemMiddleware", () => {
       expect(parsed.file_path).toBe("/app/test.c");
       expect(parsed.content).toBe("");
     });
+
+    it("all tool schema properties should be included in the required array", () => {
+      const middleware = createFilesystemMiddleware({
+        backend: () => createMockBackend(),
+      });
+
+      for (const t of middleware.tools!) {
+        const jsonSchema = (t as any).schema.toJSONSchema();
+        const properties = Object.keys(jsonSchema.properties ?? {});
+        const required = jsonSchema.required ?? [];
+
+        for (const prop of properties) {
+          expect(
+            required,
+            `tool "${(t as any).name}" is missing "${prop}" in required`,
+          ).toContain(prop);
+        }
+      }
+    });
   });
 
   describe("tool result truncation integration", () => {
diff --git a/libs/deepagents/src/middleware/fs.ts b/libs/deepagents/src/middleware/fs.ts
index 5a7e77525..f95626af5 100644
--- a/libs/deepagents/src/middleware/fs.ts
+++ b/libs/deepagents/src/middleware/fs.ts
@@ -897,6 +897,7 @@ function createGrepTool(
           .string()
           .optional()
           .nullable()
+          .default(null)
           .describe("Optional glob pattern to filter files (e.g., '*.py')"),
       }),
     },