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Dynamic Tools

Dynamic tools adapt their behavior and capabilities at runtime based on contextual input. Instead of relying on fixed configurations, they adjust to users, environments, or scenarios, enabling a single agent to serve personalized, context-aware responses.

Creating an tool​

Create a tool that fetches exchange rate data using a dynamic value provided via runtimeContext.

import { createTool } from "@mastra/core/tools";
import { z } from "zod";

export const getExchangeRatesTool = createTool({
  id: "get-exchange-rates-tool",
  description: "Gets exchanges rates for a currency",
  inputSchema: z.null(),
  outputSchema: z.object({
    base: z.string(),
    date: z.string(),
    rates: z.record(z.number()),
  }),
  execute: async ({ runtimeContext }) => {
    const currency = runtimeContext.get("currency");

    const response = await fetch(
      `https://api.frankfurter.dev/v1/latest?base=${currency}`,
    );

    const { base, date, rates } = await response.json();

    return { base, date, rates };
  },
});

See createTool() for a full list of configuration options.

Example usage​

Set RuntimeContext using set(), then call execute() passing in the runtimeContext.

import { RuntimeContext } from "@mastra/core/runtime-context";
import { getExchangeRatesTool } from "../src/mastra/tools/example-exchange-rates-tool";

const runtimeContext = new RuntimeContext();

runtimeContext.set("currency", "USD");

const result = await getExchangeRatesTool.execute({
  context: null,
  runtimeContext,
});

console.log(result);