# Free Small Biz Tools API
> Free small-business calculators from freesmallbiztools.com: quote/estimate totals (tax, discount, deposit), late-fee calculator, and the site's free-tool directory as JSON. Paid (x402 USDC on Base): $0.01 late-fee reminder email (polite/firm/final), $0.05 good/better/best quote pack with terms, and a $1 small-business tool stack report built from the directory's checked listings. MCP server at /mcp. Invoicing and automatic reminders: PaidPilot (paidpilot.io).

Payments: x402 v2, scheme "exact", USDC on Base mainnet (eip155:8453), asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913, payTo 0x2dAF658B01e257206375798a15832E9f547D65dD. No accounts or API keys.
Flow: call the paid URL -> HTTP 402 with a base64 JSON PAYMENT-REQUIRED header -> sign an EIP-3009 USDC authorization for one of `accepts` -> retry with PAYMENT-SIGNATURE -> 200 + PAYMENT-RESPONSE (settlement receipt). Invalid input returns 400 and is never charged; upstream failures return 5xx and are not settled.
Client libraries: @x402/fetch (wrapFetchWithPayment), @x402/axios, or any x402 v2 client.

## Paid endpoints
- [GET /v1/late-fee-notice](https://api.freesmallbiztools.com/v1/late-fee-notice) $0.01: Late-fee reminder email for an overdue invoice. Calculates the late fee and writes a ready-to-send reminder (subject + body) in a polite, firm or final tone. Bad input 400, never charged. Query: `amount`, `due_date`, `paid_date`, `rate`, `rate_type`, `grace_days`, `tone`, `client_name`, `business_name`, `invoice_number`. Example: https://api.freesmallbiztools.com/v1/late-fee-notice?amount=1200&due_date=2026-09-01&paid_date=2026-10-14&rate=1.5&rate_type=monthly_percent&tone=polite
- [POST /v1/quote-pack](https://api.freesmallbiztools.com/v1/quote-pack) $0.05: Good / better / best quote pack with terms and a cover note. From your line items: three priced options, deposit, validity date, standard terms and a short cover note. Bad input 400, never charged. Body: JSON (see openapi.json).
- [GET /v1/stack-report](https://api.freesmallbiztools.com/v1/stack-report) $1: Small-business free tool stack report. Picks one free or freemium tool per need for your business type from freesmallbiztools.com's checked listings (vendor quote + check date), with alternatives and caveats. business_type: service, trades, retail, online_store, creator, consultant, agency, nonprofit. Bad input 400, never charged. Query: `business_type`, `needs`, `team_size`, `free_only`. Example: https://api.freesmallbiztools.com/v1/stack-report?business_type=consultant

## Free endpoints
- POST https://api.freesmallbiztools.com/v1/quote: free: quote/estimate totals from line items (JSON body: items[{description,quantity,unit_price}], tax_percent, discount_percent, deposit_percent, valid_days, currency)
- GET https://api.freesmallbiztools.com/v1/late-fee?amount=&due_date=&paid_date=&rate=&rate_type=&grace_days=: free: late fee on an overdue invoice (simple interest, monthly/annual/daily percent or flat)
- GET https://api.freesmallbiztools.com/v1/tools: free: the directory's tools and categories as JSON (?category= to filter)
- POST https://api.freesmallbiztools.com/mcp: MCP server (streamable HTTP, stateless): free quote_totals, late_fee, list_tools, pricing; paid late_fee_notice, quote_pack, small_business_stack_report via x402 in _meta

## Discovery
- OpenAPI: https://api.freesmallbiztools.com/openapi.json
- x402 manifest: https://api.freesmallbiztools.com/.well-known/x402
- API catalog (RFC 9727): https://api.freesmallbiztools.com/.well-known/api-catalog
- Sitemap: https://api.freesmallbiztools.com/sitemap.xml

## Who runs this
Free Small Biz Tools (freesmallbiztools.com) by DME Computer Services, Omaha, Nebraska. Invoices, quote PDFs and automatic payment reminders: PaidPilot https://paidpilot.io

## Limits
Free endpoints: 30 requests per minute per IP (429 after). Nothing you send is stored.