Standalone Tools

You can create standalone tools that are not derived from controllers or RPC modules by implementing the VovkTool interface directly. createTool is a small utility that covers cases when you want to create custom tools that don’t map to existing back-end functionality and would be useful if you use LLM APIs directly, without 3rd-party libraries.

An example case would be using OpenAI Realtime API  that, by the time of writing, isn’t supported by Vercel AI SDK.

createTool accepts the following options, some of which are similar to deriveTools options:

• name: string - the name of the tool.
• title?: string - optional title for the tool. Used mainly for MCPs.
• description: string - the description of the tool.
• toModelOutput?: ToModelOutputFn<TInput, TOutput, TFormattedOutput> - optional
• inputSchema?: StandardSchemaV1 & StandardJSONSchemaV1 - optional input schema for the tool, supports the same libraries as procedure function.
• outputSchema?: StandardSchemaV1 & StandardJSONSchemaV1 - optional output schema for the tool, supports the same libraries as procedure function.
• execute: (input: TInput) => Promise<TOutput> | TOutput - the function to execute the tool logic.

import { createTool, ToModelOutput } from 'vovk';
import { z } from 'zod';
 
const sumNumbers = createTool({
  name: 'sum_numbers',
  title: 'Get Sum of two Numbers',
  description: 'Returns the sum of two numbers provided as input.',
  toModelOutput: ToModelOutput.MCP,
  inputSchema: z.object({
    a: z.number().description('The first number to sum.'),
    b: z.number().description('The second number to sum.'),
  }),
  outputSchema: z.number().description('The sum of the two numbers.'),
  execute({ a, b }) {
    return a + b;
  },
});
 
console.log('Standalone tool:', sumNumbers); // { name, description, parameters, execute, inputSchema, outputSchema }

The standalone tool can be merged with derived tools or used independently.

// ...
const { tools: derivedTools } = deriveTools({
  modules: { UserController },
});
 
const allTools = [...derivedTools, sumNumbers];

The sumNumbers tool can now be used like any other derived tool with name, description, parameters, and execute function, but also mirrors inputSchema and outputSchema.

Note that a derived tool includes inputSchemas as a record of procedure input, while standalone tool provides inputSchema.

See Realtime UI / Voice AI Chat for more info.