PromptKit

PromptKit is a lightweight toolkit for managing prompts in your LLM agents.

• Load prompts from files into memory at application startup.
• Supports both plain text prompts and structured chat message formats.
• Inject variables dynamically into prompts using {{variable}} syntax. Supports both global and prompt-specific variables.
• Organize prompts in directories and subdirectories for better management.

Installation

npm install prompt-toolkit

Usage

Basic Setup

import { PromptKit } from "prompt-toolkit";

// Create a PromptKit instance
const prompts = new PromptKit({
    // OPTIONAL: global variables to inject into all prompts
    variables: {
        app: "Bastion",
        ver: "10.0.0",
    },
});

Text Prompts

Create a text prompt file (e.g., prompts/system.md):

You are a helpful assistant for {{app}} version {{ver}}.

const prompt = prompts.get("system");
// "You are a helpful assistant for Bastion version 10.0.0."

// Override variables per prompt
const customPrompt = prompts.get("system", { ver: "10.17.0" });
// "You are a helpful assistant for Bastion version 10.17.0."

Chat Prompts

Create a chat prompt file (e.g., prompts/chat.json):

[
    {
        "role": "system",
        "content": "You are a helpful assistant for {{app}}."
    },
    {
        "role": "developer",
        "content": "User's name is {{user}}."
    }
]

Or use YAML (e.g., prompts/chat.yaml):

- role: system
  content: You are a helpful assistant for {{app}}.
- role: developer
  content: User's name is {{user}}.

const messages = prompts.get("chat", { user: "Alice" });
// [
//   { role: "system", content: "You are a helpful assistant for Bastion." },
//   { role: "developer", content: "User's name is Alice." }
// ]

Directory Structure

Prompts can be organized in subdirectories:

prompts/
  ├── system.md
  ├── chat.json
  └── nested/
      └── skills.md
      └── suggestions.md

prompts.get("system");           // From prompts/system.md
prompts.get("chat");             // From prompts/chat.json
prompts.get("nested/skills");    // From prompts/nested/skills.md

Methods

get(name, variables?)

Get a compiled prompt by name.

const prompt = prompts.get("system");
const customPrompt = prompts.get("system", { variable: "value" });

Returns:

• string for text prompts
• ChatMessage[] for chat prompts
• undefined if prompt doesn't exist

has(name)

Check if a prompt exists.

if (prompts.has("system")) {
    const prompt = prompts.get("system");
}

list()

List all available prompt names.

const names = prompts.list();
// [ "system", "chat", "nested/skills", "nested/suggestions" ]

reload()

Reload all prompts and update the in-memory cache.

prompts.reload();

Variable Substitution

Variables use the {{variableName}} syntax:

// Template: "Hello {{name}}, welcome to {{product}}!"
prompts.get("welcome", { name: "Alice", product: "Omnic" });
// "Hello Alice, welcome to Omnic!"

Unmatched variables remain as-is in the output.

License

MIT