diff --git a/src/json.h b/src/json.h
new file mode 100644
index 0000000..c24f1a8
--- /dev/null
+++ b/src/json.h
@@ -0,0 +1,33 @@
+/*
+ * This file is part of the Pico Keys SDK distribution (https://github.com/polhenarejos/pico-keys-sdk).
+ * Copyright (c) 2022 Pol Henarejos.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef _JSON_H_
+#define _JSON_H_
+
+#include "cJSON.h"
+
+#define CJSON_ADD_GENERIC(hdl, ptr, item, value) do { \
+    if (hdl(ptr, item, value) == NULL) { \
+        response->status_code = 500; \
+        return 1; \
+    } \
+} while(0)
+
+#define CJSON_ADD_STRING(ptr, item, value) CJSON_ADD_GENERIC(cJSON_AddStringToObject, (ptr)->json, item, value)
+#define CJSON_ADD_NUMBER(ptr, item, value) CJSON_ADD_GENERIC(cJSON_AddNumberToObject, (ptr)->json, item, value)
+
+#endif // _JSON_H_