diff --git a/docs/en/sdks/JS-sdk/adk/index.md b/docs/en/sdks/JS-sdk/adk/index.md
index d64a1c1d34..94267660cb 100644
--- a/docs/en/sdks/JS-sdk/adk/index.md
+++ b/docs/en/sdks/JS-sdk/adk/index.md
@@ -87,12 +87,16 @@ The SDK supports multiple transport protocols to communicate with the Toolbox se
 
 ### Available Protocols
 
+{{< notice note >}}
+The native Toolbox protocol (`Protocol.TOOLBOX`) is deprecated and will be removed on March 4, 2026. Please use `Protocol.MCP` or specific MCP versions.
+{{< /notice >}}
+
 - `Protocol.MCP`: The default protocol version (currently aliases to `MCP_v20250618`).
 - `Protocol.MCP_v20241105`: Use this for compatibility with older MCP servers (November 2024 version).
 - `Protocol.MCP_v20250326`: March 2025 version.
 - `Protocol.MCP_v20250618`: June 2025 version.
 - `Protocol.MCP_v20251125`: November 2025 version.
-- `Protocol.TOOLBOX`: Legacy Toolbox protocol.
+- `Protocol.TOOLBOX`: **Deprecated** Legacy Toolbox protocol.
 
 ### Specifying a Protocol