diff --git a/agent/tool_schema.json b/agent/tool_schema.json
new file mode 100644
index 0000000..3f0d0f8
--- /dev/null
+++ b/agent/tool_schema.json
@@ -0,0 +1,19 @@
+{
+  "name": "get_customer_activity_summary",
+  "description": "Return a de-identified financial activity summary for a customer, identified ONLY by an opaque token (e.g. CUST_000123). Never accepts or returns a name.",
+  "inputSchema": {
+    "type": "object",
+    "properties": {
+      "customer_token": {
+        "type": "string",
+        "description": "Opaque customer token, e.g. CUST_000123. Pass verbatim."
+      },
+      "period_days": {
+        "type": "integer",
+        "description": "Look-back window in days.",
+        "default": 90
+      }
+    },
+    "required": ["customer_token"]
+  }
+}