diff --git a/src/main/java/dev/selimaj/session/types/HandlerResult.java b/src/main/java/dev/selimaj/session/types/HandlerResult.java
new file mode 100644
index 0000000..d2eaf00
--- /dev/null
+++ b/src/main/java/dev/selimaj/session/types/HandlerResult.java
@@ -0,0 +1,6 @@
+package dev.selimaj.session.types;
+
+import com.fasterxml.jackson.databind.JsonNode;
+
+public record HandlerResult(boolean isError, JsonNode value) {
+}
diff --git a/src/main/java/dev/selimaj/session/types/MethodHandler.java b/src/main/java/dev/selimaj/session/types/MethodHandler.java
new file mode 100644
index 0000000..46ea0b3
--- /dev/null
+++ b/src/main/java/dev/selimaj/session/types/MethodHandler.java
@@ -0,0 +1,10 @@
+package dev.selimaj.session.types;
+
+import com.fasterxml.jackson.databind.JsonNode;
+
+import java.util.concurrent.CompletableFuture;
+
+@FunctionalInterface
+public interface MethodHandler {
+    CompletableFuture<HandlerResult> handle(int id, JsonNode data);
+}