FreeToolHub

Model Context Protocol

FreeToolHub MCP Server

Give your AI agent 44 calculators — US tax, finance and business (payroll deductions, sales tax rates, economic nexus, dropshipping and reseller profit, mortgage, 401(k) vs Roth, capital gains), plus an MCP engineering suite that audits your own agent setup: context-window budgeting, tool-description compression, server trust scoring, OWASP MCP security auditing and token cost attribution. Your agent calls them directly; results come back as structured JSON. Free, no signup, no API key required.

Endpoint ↗https://freetoolhub.org/api/mcp

Quick start

Pick your client. The server speaks Streamable HTTP, so there is nothing to install and no local process to run.

Claude Code

terminal
claude mcp add --transport http freetoolhub https://freetoolhub.org/api/mcp

Cursor

Add to ~/.cursor/mcp.json (or project-level .cursor/mcp.json).

json
{
  "mcpServers": {
    "freetoolhub": {
      "url": "https://freetoolhub.org/api/mcp"
    }
  }
}

Any other MCP client

Windsurf, Cline, Zed, Claude Desktop and the rest all accept the same shape.

json
{
  "mcpServers": {
    "freetoolhub": {
      "type": "http",
      "url": "https://freetoolhub.org/api/mcp"
    }
  }
}

Available calculators (27)

Every calculator below is also available as a page on this site — the MCP tool and the web tool share the same formulas and the same live datasets.

Tax12

  • calculate_se_taxweb version ↗

    Calculate US self-employment tax (15.3%), QBI deduction, quarterly payments. Uses latest IRS brackets from CDN data.

    Parameters: netEarnings*, filingStatus, state(* required)

  • calculate_freelancer_taxweb version ↗

    Complete freelancer tax: SE tax, QBI deduction, federal + state income tax. Returns quarterly payment. Uses latest CDN data.

    Parameters: grossIncome*, businessExpenses, filingStatus, state(* required)

  • calculate_1099k_taxweb version ↗

    Estimate tax on 1099-K income (reselling, gig work). SE tax, QBI, quarterly 1040-ES. Uses latest CDN data.

    Parameters: grossReceipts*, costOfGoodsSold, otherExpenses, filingStatus, state(* required)

  • calculate_capital_gains_taxweb version ↗

    US capital gains tax on stock/crypto. Short vs long-term, NIIT 3.8%, state tax. Uses latest CDN LTCG brackets.

    Parameters: purchasePrice*, salePrice*, holdingPeriodDays*, filingStatus, ordinaryIncome, state(* required)

  • compare_w2_vs_1099web version ↗

    Compare take-home pay: W-2 salary vs 1099 contractor rate. SE tax, FICA, standard deduction, state tax. Latest CDN data.

    Parameters: w2Salary*, contractorRate*, filingStatus, state(* required)

  • get_sales_tax_rateweb version ↗

    Get state sales tax rate for any US state. Returns base state rate + estimated local rate. Latest CDN data.

    Parameters: state*, amount(* required)

  • calculate_payroll_taxweb version ↗

    Calculate paycheck deductions: federal tax, Social Security, Medicare, state tax. All 50 states. Latest CDN data.

    Parameters: grossSalary*, filingStatus, state, retirementContribution(* required)

  • calculate_estate_taxweb version ↗

    Calculate federal estate tax. 2026 exemption $13.61M, 40% rate. Includes marital deduction.

    Parameters: estateValue*, spousalInheritance(* required)

  • calculate_hsa_fsa_savingsweb version ↗

    Calculate tax savings from HSA and FSA contributions. Federal + FICA + state tax savings. Latest CDN limits.

    Parameters: hsaContribution, fsaContribution, filingStatus, state, marginalRate(* required)

  • calculate_quarterly_taxweb version ↗

    Calculate quarterly estimated tax payments (Form 1040-ES). SE tax + income tax divided by 4. Latest CDN data.

    Parameters: annualIncome*, businessExpenses, filingStatus, state(* required)

  • check_economic_nexusweb version ↗

    Check which US states you have economic nexus in for sales tax collection. Based on Wayfair ruling. Latest CDN thresholds.

    Parameters: totalSales*, statesWithSales(* required)

  • calculate_tariffweb version ↗

    Estimate import duties and landed cost by HS code category. Covers US MFN + Section 301 tariffs.

    Parameters: productValue*, freight, tariffRate, category(* required)

Finance10

  • calculate_compound_interestweb version ↗

    Compound interest with monthly contributions. Returns final balance, total interest, inflation-adjusted value. Uses latest CDN inflation rate.

    Parameters: principal*, monthlyContribution, annualRate*, years*, inflationRate(* required)

  • calculate_mortgageweb version ↗

    Monthly mortgage payment (P&I) + property tax, insurance, PMI. Full PITI breakdown. Uses latest CDN mortgage rates for defaults.

    Parameters: homePrice*, downPayment*, interestRate, loanTermYears, propertyTaxRate, insuranceRate(* required)

  • compare_401k_vs_rothweb version ↗

    Compare 401(k) pre-tax vs Roth IRA post-tax. 30-year growth, tax drag, recommendation. Uses latest CDN contribution limits.

    Parameters: annualContribution*, currentTaxRate*, retirementTaxRate*, annualReturn, years, employerMatch(* required)

  • calculate_car_loanweb version ↗

    Monthly car payment, total interest, amortization. Includes sales tax, trade-in, down payment. Uses latest CDN sales tax rates.

    Parameters: price*, downPayment, tradeIn, interestRate*, loanTermMonths, salesTaxRate, state(* required)

  • calculate_rental_roiweb version ↗

    Rental property ROI: cap rate, cash-on-cash return, NOI, annual cash flow. Includes vacancy and management.

    Parameters: propertyValue*, monthlyRent*, downPayment*, interestRate, vacancyRate, managementRate(* required)

  • calculate_student_loanweb version ↗

    Student loan payoff: monthly payment, total interest, months saved with extra payments.

    Parameters: loanAmount*, interestRate*, loanTermYears, extraPayment(* required)

  • calculate_roiweb version ↗

    ROI, ROAS, net profit, CPA, CPC for marketing campaigns. Facebook, Google, TikTok ad analysis.

    Parameters: revenue*, cost*, adSpend, clicks, conversions(* required)

  • calculate_life_insuranceweb version ↗

    Calculate life insurance needs using DIME method: Debt, Income, Mortgage, Education.

    Parameters: annualIncome*, yearsToReplace, debt, mortgage, collegeFund, children, savings(* required)

  • calculate_rental_affordabilityweb version ↗

    How much rent can you afford? 30% rule, DTI ratio, comfortable rent range.

    Parameters: monthlyIncome*, monthlyDebts(* required)

  • calculate_home_equityweb version ↗

    Calculate home equity, max borrowable amount (HELOC), and monthly payments. LTV limits included.

    Parameters: homeValue*, mortgageBalance*, interestRate, loanTermYears(* required)

Business5

  • calculate_break_evenweb version ↗

    Break-even point: units to sell to cover fixed costs. Contribution margin, target profit analysis.

    Parameters: fixedCosts*, pricePerUnit*, variableCostPerUnit*, targetProfit(* required)

  • compare_llc_costweb version ↗

    Compare LLC formation and maintenance costs across US states. 5-year total cost. Uses latest CDN LLC state fees data.

    Parameters: state, years(* required)

  • calculate_dropship_profitweb version ↗

    True dropshipping profit after product cost, platform fees, payment processing, ad spend. Uses latest CDN payment processor fees.

    Parameters: salePrice*, productCost*, adSpendPerOrder*, shippingCost, platform, paymentProcessor(* required)

  • calculate_reseller_profitweb version ↗

    Compare real profit across reselling platforms (eBay, Poshmark, Mercari, etc.) after fees. Uses latest CDN platform fee data.

    Parameters: purchasePrice*, salePrice*, shippingCost, state(* required)

  • calculate_freelancer_pricingweb version ↗

    Turn hourly rate into project quote with overhead, profit margin, milestone splits.

    Parameters: hourlyRate*, projectHours*, overheadPct, profitMarginPct(* required)

Example call

The transport is plain JSON-RPC over HTTP, so you can test it from a terminal before wiring it into a client.

request
curl -s https://freetoolhub.org/api/mcp \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "calculate_payroll_tax",
      "arguments": { "grossSalary": 85000, "filingStatus": "single", "state": "CA" }
    }
  }'
response
{
  "gross": 85000,
  "ssTax": 5270,
  "medicare": 1232.5,
  "fedTax": 9842.5,
  "stateTax": 3100,
  "retirement": 6000,
  "takeHome": 63651,
  "monthly": 5304.25,
  "_meta": {
    "source": "FreeToolHub.org — Free Tools",
    "webUrl": "https://freetoolhub.org/payroll-tax-calculator"
  }
}

Limits & data freshness

  • 50 tool calls per day, per IP — free, no account, no API key. tools/list is not rate limited, so agents can discover tools freely.
  • No daily cap with a licence key — send your key in the X-API-Key header and the per-IP daily limit no longer applies. Every response reports your tier under _meta.rateLimit.tier.
    with a licence key
    curl -s https://freetoolhub.org/api/mcp \
  -H 'Content-Type: application/json' \
  -H 'X-API-Key: YOUR-LICENSE-KEY' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'
    The key is the licence key from your Pro purchase — there is nothing extra to generate. It is validated against Creem and cached for 10 minutes; an unrecognised key is reported as an error rather than silently downgraded.
  • Tax brackets, contribution limits, state rates and platform fees are served from the same live datasets as the web tools. Every response carries a _meta.dataFreshness block with the source and last-updated date — see the methodology page.
  • Results are estimates for planning, not tax advice. Verify anything you file with a qualified professional.