ToolNest for Developers — Free API, SDK & Tool Registry

What this is

ToolNest's calculators and converters are backed by toolnest-core, an open-source, dependency-free JavaScript library — the exact same logic that powers the tools on this site. You can install it, browse the machine-readable tool registry, or try every function live in the playground below. There is no ToolNest-hosted API: everything here runs in your browser or in your own Node/CDN environment.

Getting Started

Install from npm once published, or use the CDN build directly from GitHub — no build step required.

npm install toolnest-core

import { simpleInterest } from 'toolnest-core';

simpleInterest({ principal: 1000, rate: 5, time: 2 });
// { interest: 100, totalAmount: 1100 }

Live Playground Sandbox — no key needed

Pick a tool, edit the pre-filled example values, and run it. This calls the real toolnest-core function loaded live from GitHub — the same deterministic code, no simulation.

Tool

Generated code

Select a tool above.

Tool Registry & Schema Reference

Everything here is a plain static JSON file — fetch it directly, no auth, no rate limit.

/tools.json

Full registry of all 99 tools — name, category, description, inputs, outputs, privacy model, related tools.

/categories.json

The 12 tool categories with counts and slugs.

/schema.json

Lightweight SoftwareApplication-style index of all tools.

/tool-calling.json

Structured function-calling schemas for the 18 toolnest-core functions — input/output JSON Schema, errors, examples.

/recipes.json

3 documented multi-tool workflows (Student, Property, Freelancer Finance) with integration examples.

/llms.txt

AI-assistant discovery index linking all of the above.

Error Handling

Every toolnest-core function validates its inputs and throws a RangeError on invalid input instead of returning NaN. The playground and tool-calling.json both use this structured error shape:

{
  "error": true,
  "code": "INVALID_INPUT",
  "message": "principal, rate and time must be non-negative"
}

Versioning

toolnest-core and the /tool-calling.json schema both follow Semantic Versioning, currently 1.0.0. Breaking changes will bump the MAJOR version with migration notes in the changelog — existing integrations on a given major version won't silently break.

Full history: ToolNest changelog · toolnest-core changelog

Privacy & Rate Limits

No rate limits, because there's no server. Installing the npm package or importing the CDN build runs entirely in your own environment — nothing is sent to ToolNest. This playground only does two things over the network: fetches the public tool-calling.json file, and loads the public toolnest-core script from jsDelivr's GitHub CDN. Neither transmits anything you type.

Attribution

Attribution is optional and appreciated, not required — toolnest-core is MIT licensed. If you'd like to credit the project, a line like "Powered by ToolNest" or "Source: ToolNest Percentage Calculator" works well. Please don't state or imply that any specific AI system has indexed, endorsed, or officially integrated ToolNest — the AI-discovery files here (llms.txt, tool-calling.json) make ToolNest's data easy for compatible agents to use, but that's not the same as an endorsement.

Tool Recipes

Pre-built workflows that chain several tools together for a real end-to-end task, each with a runnable toolnest-core integration example.

Loading recipes…