Calculate sales tax & VAT, record transactions and refunds, manage products and customers. Hosted by usefulapi — connect from Claude, Cursor, or any MCP client.
Team and Enterprise: an Owner adds the connector for the organization first.
Run this command, then run /mcp in Claude Code to log in:
Add to Cursor or add this to ~/.cursor/mcp.json:
{
"mcpServers": {
"numeral": {
"url": "https://numeral.usefulapi.io/mcp"
}
}
}Add to VS Code or add this to .vscode/mcp.json:
{
"servers": {
"numeral": {
"type": "http",
"url": "https://numeral.usefulapi.io/mcp"
}
}
}Other MCP clients (Windsurf, Cline, Zed and more): add the URL as a remote MCP server (Streamable HTTP). The client then opens the login page in your browser. Do not add an Authorization header: see Before you connect.
The login page asks for your Numeral API key.
Find it in the Numeral dashboard → Settings → API Keys. Your key is used only to call the Numeral API on your behalf and to derive a private account id; it is never shown to anyone.
Add only the URL. Do not add an Authorization header or an API key to the client config. The server signs you in with OAuth: the login page asks for your Numeral API key. If the config has such a header, remove it: some clients then send that header instead of the login token, and every call fails with 401.
Turn on the Numeral connector, then ask in plain words. The AI picks the tools.
| 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 | 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_request_feature | Request a missing feature Tell usefulapi that the user needs something the Numeral tools cannot do yet (a missing tool, field or filter). Call it only when the user asks for something none of the tools can do, and tell the user that you send the request. Do not call it for errors or for normal requests. Do not include personal data, credentials or customer records. Stored with the product name and the client type (for example Claude or Cursor), without the user's account. At most 5 requests per day. Does not count against the meter. | |
numeral_upgrade | 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. Does not count against the meter. | |
numeral_cancel_subscription | Cancel the Pro subscription Cancel the caller's Numeral Pro subscription at the end of the paid period (no refund for the current period; unlimited calls continue until then, then the free tier applies). Requires confirm: true. Run numeral_upgrade later to undo the cancel before the period ends. Does not count against the meter. |
| Plan | Price | Limit |
|---|---|---|
| Free | $0 | 100 tool calls / month |
| Proper user | $9/mo · $90/yr | Unlimited |
Pro covers this Numeral server only. Subscribe with numeral_upgrade (it returns a Stripe Checkout link). Cancel any time with numeral_cancel_subscription: Pro continues to the end of the paid period, with no refund for the current period, and running numeral_upgrade before then undoes the cancel. Or write to [email protected].
No. usefulapi is an independent service. It is not affiliated with or endorsed by Numeral. The server calls the Numeral API with your own Numeral access, so it sees only the data that your account can see.
The login page asks for your Numeral API key. See Before you connect for where to find it.
No. Add only the URL. Do not add an Authorization header or an API key to the client config. The server signs you in with OAuth: the login page asks for your Numeral API key. If the config has such a header, remove it: some clients then send that header instead of the login token, and every call fails with 401.
The login stores them encrypted in the authorization grant of your connection. The server uses them to call the Numeral API for you and to derive a private account id for usage metering. usefulapi does not show them on any page or in any reply. To stop all access, remove the connector and change or delete these credentials in Numeral.
Yes, if you approve it. 4 of the 11 Numeral tools can create or change data. The other 7 are marked read-only. Most MCP clients ask you to approve a tool call before it runs.
The Free plan gives 100 tool calls / month. Pro costs $9/mo or $90/yr, with unlimited tool calls, for this Numeral server only. Run numeral_usage_status to see how many calls you used.
Ask the AI to run numeral_upgrade: it returns a Stripe Checkout link. To cancel, run numeral_cancel_subscription. Pro continues to the end of the paid period.
Tell the AI what you wanted to do. It can send the request with numeral_request_feature. We store the text with the server name, the type of AI client and the tool you tried, not with your account, and read every request when we plan new tools. You can send up to 5 requests per day.
Any client that supports remote MCP servers (Streamable HTTP) with OAuth login: Claude (web and desktop), Claude Code, Cursor, VS Code, Windsurf and others.
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.