MCP Toolbox for Databases

--- title: "Javascript" type: docs weight: 2 description: > How to add pre- and post- processing to your Agents using JS. --- ## Prerequisites This tutorial assumes that you have set up MCP Toolbox with a basic agent as described in the [local quickstart](../../getting-started/local_quickstart_js.md). This guide demonstrates how to implement these patterns in your Toolbox applications. ## Implementation {{< tabpane persist=header >}} {{% tab header="ADK" text=true %}} The following example demonstrates how to use the `beforeToolCallback` and `afterToolCallback` hooks in the ADK `LlmAgent` to implement pre and post processing logic. ```js {{< include "js/adk/agent.js" >}} ``` You can also add model-level (`beforeModelCallback`, `afterModelCallback`) and agent-level (`beforeAgentCallback`, `afterAgentCallback`) hooks to intercept messages at different stages of the execution loop. For more information, see the [ADK Callbacks documentation](https://google.github.io/adk-docs/callbacks/types-of-callbacks/). {{% /tab %}} {{% tab header="Langchain" text=true %}} The following example demonstrates how to use `ToolboxClient` with LangChain's middleware to implement pre and post processing for tool calls. ```js {{< include "js/langchain/agent.js" >}} ``` You can also use the `wrapModelCall` hook to intercept messages before and after model calls. You can also use [node-style hooks](https://docs.langchain.com/oss/javascript/langchain/middleware/custom#node-style-hooks) to intercept messages at the agent and model level. See the [LangChain Middleware documentation](https://docs.langchain.com/oss/javascript/langchain/middleware/custom#tool-call-monitoring) for details on these additional hook types. {{% /tab %}} {{< /tabpane >}} ## Results The output should look similar to the following. {{< notice note >}} The exact responses may vary due to the non-deterministic nature of LLMs and differences between orchestration frameworks. {{< /notice >}} ``` AI: Booking Confirmed! You earned 500 Loyalty Points with this stay. AI: Error: Maximum stay duration is 14 days. ```