Tool Rendering - Copilotkit

<Callout> This example demonstrates the [implementation](#implementation) section applied in the{" "} <a href="https://feature-viewer.copilotkit.ai/langgraph/feature/agentic_chat" target="_blank" > CopilotKit feature viewer </a> . </Callout>

What is this?

Tools are a way for the LLM to call predefined, typically, deterministic functions. CopilotKit allows you to render these tools in the UI as a custom component, which we call Generative UI.

When should I use this?

Rendering tools in the UI is useful when you want to provide the user with feedback about what your agent is doing, specifically when your agent is calling tools. CopilotKit allows you to fully customize how these tools are rendered in the chat.

Implementation

<Steps> <Step> ### Run and connect your agent <RunAndConnect /> </Step> <Step> ### Give your agent a tool to call

The agent in the live demo above exposes a mock get_weather tool. This is the definition straight from the Python backend:

<Snippet region="weather-tool-backend" /> </Step> <Step> ### Render the tool call in your frontend

At this point, your agent will be able to call the get_weather tool. Now we just need to add a useRenderTool hook to render the tool call in the UI.

<Callout type="info" title="Important"> In order to render a tool call in the UI, the name must match the name of the tool. </Callout>

The example below uses a branded <WeatherCard /> component to render the call — same pattern as the minimal example above, just wired to a richer UI:

<Snippet region="render-weather-tool" /> </Step> <Step> ### Add a catch-all renderer (optional)

For every other tool the agent calls, a single useDefaultRenderTool hook can provide a uniform fallback UI — this is exactly how the demo above handles get_stock_price, roll_dice, and any tool the agent might add later without a dedicated renderer:

<Snippet region="catchall-renderer" /> </Step> <Step> ### Give it a try!

Try asking the agent to get the weather for a location. You should see the custom UI component that we added render the tool call and display the arguments that were passed to the tool.

</Step> </Steps>

Default Tool Rendering