usefulapi

Numeral MCP server. Calculate sales tax & VAT, record transactions and refunds, manage products and customers.

Claude

Open Settings → Connectors → Add custom connector
Paste this URL:
https://numeral.usefulapi.io/mcp
Authenticate with Numeral when prompted

Cursor · VS Code · Windsurf · Cline

Add to your MCP config, then reload & authorize:

{
  "mcpServers": {
    "numeral": {
      "url": "https://numeral.usefulapi.io/mcp"
    }
  }
}

live13 toolsFree 100 tool calls / monthPro $9/mo · $90/yr

Tools 13

Tool	Type	What it does
`numeral_ping`	read	Ping (health check) Health check — verifies the API key works and reports the environment (test/prod), api_version, and server timestamp. Numeral: GET /tax/ping.
`numeral_calculate_tax`	read	Calculate tax Calculate sales tax / VAT for an order — a STATELESS quote that persists nothing (record it later with numeral_create_transaction using the returned calculation id). Returns per-jurisdiction rates, total_tax_amount, and totals. Provide a customer address and one or more line items (each needs reference_product_id OR product_category). Amounts are in the currency's smallest unit (cents). Numeral: POST /tax/calculations.
`numeral_get_transaction`	read	Get transaction Get a recorded transaction by its Numeral id (tr_...). Returns the transaction with its line items, currencies, and metadata. Numeral: GET /tax/transactions/{transaction_id}.
`numeral_list_transaction_refunds`	read	List transaction refunds List all refunds recorded against a transaction. Returns {refunds:[...]}. Numeral: GET /tax/transactions/{transaction_id}/refunds.
`numeral_list_products`	read	List products List your Numeral products (up to 50 per page), each with its reference id, name, and product_category. Use `cursor` (the last_product_id from a previous page) to paginate; has_more indicates more pages. Numeral: GET /tax/products.
`numeral_get_product`	read	Get product Get a single product by its reference_product_id (your id). Returns the product's name, product_category, and timestamps. Numeral: GET /tax/products/{reference_product_id}.
`numeral_get_customer`	read	Get customer Get a customer by id. By default `customer_id` is the Numeral id (cus_...); set id_type to "reference" to look up by your own reference_customer_id. Returns name, email, and tax-exempt status. Numeral: GET /tax/customers/{customer_id}.
`numeral_create_transaction`	write	Create transaction RECORDS a completed sale as a transaction — this WRITES a live tax/compliance record used for filings. Supply the `calculation_id` returned by numeral_calculate_tax and your `reference_order_id`. Numeral: POST /tax/transactions.
`numeral_create_refund`	write	Create refund RECORDS a refund against a transaction — this WRITES a live tax/compliance record (adjusts tax owed). Use type="full" to refund the whole transaction, or type="partial" with line_items (each keyed by reference_product_id) for a partial refund. Numeral: POST /tax/refunds.
`numeral_create_product`	write	Create product CREATES (or upserts) a product with its tax category — this WRITES to your Numeral product catalog, which drives future tax calculations. Numeral: POST /tax/products.
`numeral_create_customer`	write	Create customer CREATES a customer record — this WRITES to your Numeral customer list (used for order tracking and tax exemptions). Numeral: POST /tax/customers.
`numeral_usage_status`	meta	Usage status (free-tier meter) Report the caller's current free-tier usage this month: calls used, monthly limit, remaining, and whether the cap is reached. Read-only; does not count against the meter.
`numeral_upgrade`	meta	Upgrade to Pro (unlimited) Subscribe to the Pro plan for UNLIMITED Numeral tool calls (the free tier caps monthly usage). Choose monthly ($9/month) or yearly ($90/year — 2 months free) billing. Returns a Stripe Checkout link to open in your browser; after payment your account upgrades automatically. Read-only; does not count against the meter.

Pricing

Plan	Price	Limit
Free	$0	100 tool calls / month
Proper user	$9/mo · $90/yr	Unlimited

This is a Model Context Protocol endpoint — meant to be connected from an AI client, not opened in a browser. An invalid_token response at the URL is the auth gate working as designed; clients authenticate automatically.