REST API3 min

How to call ToolKnife API from JavaScript/Node.js

Integrate ToolKnife tools into your JavaScript or Node.js application with fetch. No SDK needed.

Prerequisites

  • Node.js 18+ (or any modern browser)
1

Make your first API call

Use the native `fetch` API. No SDK or package needed. Works in Node.js 18+, Deno, Bun, and all modern browsers.
calculate-bmi.ts
const response = await fetch(
  "https://toolknife.com/api/v1/tools/bmi-calculator_calculate",
  {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ weightKg: 75, heightCm: 180 }),
  }
);

const { result } = await response.json();
console.log(`BMI: ${result.bmi}, Category: ${result.category}`);
// BMI: 23.15, Category: Normal weight
2

Create a reusable client

Wrap the API in a simple function for cleaner code. No need for an npm package when fetch does the job.
toolknife.ts
const TOOLKNIFE_API = "https://toolknife.com/api/v1/tools";

async function callTool<T>(
  slug: string,
  params: Record<string, unknown>,
  apiKey?: string
): Promise<T> {
  const headers: Record<string, string> = {
    "Content-Type": "application/json",
  };
  if (apiKey) headers["x-api-key"] = apiKey;

  const res = await fetch(`${TOOLKNIFE_API}/${slug}`, {
    method: "POST",
    headers,
    body: JSON.stringify(params),
  });

  if (!res.ok) {
    throw new Error(`ToolKnife API error: ${res.status} ${res.statusText}`);
  }

  const data = await res.json();
  return data.result as T;
}

// Usage
const bmi = await callTool<{ bmi: number; category: string }>(
  "bmi-calculator_calculate",
  { weightKg: 75, heightCm: 180 }
);
3

Build a multi-tool workflow

Chain tools together for complex calculations. This example builds a SaaS metrics dashboard.
saas-metrics.ts
// SaaS metrics from raw business data
const [mrr, churn, ltv] = await Promise.all([
  callTool("mrr-arr-calculator_calculate", {
    subscribers: 250,
    avgMonthlyRevenue: 49,
  }),
  callTool("churn-rate-calculator_calculate", {
    startCustomers: 250,
    lostCustomers: 12,
    period: "monthly",
  }),
  callTool("ltv-calculator_calculate", {
    avgRevenue: 49,
    churnRate: 4.8,
  }),
]);

console.log({ mrr, churn, ltv });
4

Use in Next.js Server Components

ToolKnife API calls work great in Next.js Server Components and Route Handlers. The response is cacheable.
app/mortgage/page.tsx (Next.js)
export default async function MortgagePage() {
  const res = await fetch(
    "https://toolknife.com/api/v1/tools/mortgage-calculator_monthly-payment",
    {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({
        principal: 360000,
        annualRate: 6.5,
        years: 30,
      }),
      next: { revalidate: 3600 }, // Cache for 1 hour
    }
  );

  const { result } = await res.json();

  return (
    <div>
      <p>Monthly payment: ${result.monthlyPayment.toFixed(2)}</p>
    </div>
  );
}
5

Add authentication

Pass your API key in the `x-api-key` header. Get your key at toolknife.com/dashboard/api-keys.
With API key
const result = await callTool(
  "currency-converter_convert",
  { amount: 1000, from: "USD", to: "EUR" },
  process.env.TOOLKNIFE_API_KEY // "tk_..."
);

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Tools used in this guide

bmi-calculatormrr-arr-calculatormortgage-calculator

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