node.jsopen in new window Coverage Statusopen in new window npm versionopen in new window

A package that provides simplified base components to make building and maintaining LLM-powered applications easier.

  • Write functions powered by LLM's with easy to use building blocks.
  • Pure Javascript and Typescript. Allows you to pass and infer types.
  • Not very opinionated. You have control on how you use it.
  • Support for text-based and chat-based prompts (gpt-3.5-turbo and gpt-4).
  • Supercharge your prompts by using handlebars within prompt template.
  • Allow LLM's to call functions (or call other LLM executors).

Core Components


LLM is a wrapper around various LLM providers.

  • Built-in retry with configurable timeout.
  • Configurable back-off mechanism.
  • Use different llms with different configurations for different functions.


A prompt is a plain-text instruction for the llm to process. While a prompt is ultimately just a string, constructing elaborate prompts that are maintainable, reusable, and generally easy to work with can become complex.

  • Uses handlebars as template engine, allowing you to use features such as custom templates, partials, functions, etc. See handlebars documentation.


Parsers are used to parse LLM responses.

Example default parsers are:

  • JSON: will try to parse a string response that contains JSON to a plain object. You can pass schema (Schema spec) to infer typings, provide validation, and set defaults.
  • List to array: Will take text separated with /n and return an array of strings.
  • Number: will enforce a number from the response.

Llm Executor

Llm-powered functions take an llm, prompt, and optionally a parser, and wrap in a well-typed executor function. These can be used to call an llm with the input passed at the time of execution.

Callable Executors

Callable executors are a wrapper around core executors, which add a few extra properties, and make them callable from an llm.

CallableCoreFunction - class that takes a function or pipeline and makes it callable by an llm by adding some properties, createCallableCoreFunction - helper function that returns a new CallableCoreFunction instance

UseFunctions - class that is provided an array of callable functions, and provides an interface to easily call them, and get info about them, etc. useFunctions - helper function that returns a new UseFunctions instance

Core Functions

Core functions are the base of an llm function. Only advanced uses will require using (or extending) core functions directly. You may notice that you use core functions indirectly, as any normal function passed into pipeline, or callable function, will be wrapped internally as a core function. createLlmExecutor- helper function, returns new LlmExecutor instance

Core functions are a class that provides a unified interface for calling llm and non-llm powered functions. createCoreExecutor - helper function, returns new CoreExecutor instance

Last Updated:
Contributors: Greg Reindel