Read smallinvoice contacts, invoices, offers, projects and hours; create contacts and invoices. Hosted by usefulapi — connect from Claude, ChatGPT, 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": {
"smallinvoice": {
"url": "https://smallinvoice.usefulapi.io/mcp"
}
}
}Add to VS Code or add this to .vscode/mcp.json:
{
"servers": {
"smallinvoice": {
"type": "http",
"url": "https://smallinvoice.usefulapi.io/mcp"
}
}
}No Add custom MCP server option? It depends on your account or workspace settings: see OpenAI's guide.
Run these commands. The second one opens the login page:
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 Client ID and Client secret.
Create the client yourself in smallinvoice: Home → Users → API V2, new client, grant type Client credentials, and tick the scopes you want to give the assistant (contact, invoice, offer, order confirmation, delivery note, catalog, configuration, project, working hours, effort, activity, cost unit). Create a client just for this connection, so you can delete it there at any time. The secret is used only to get smallinvoice access tokens and call the API on your behalf; it is never shown to anyone. Documents and contacts contain your customers' personal data.
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 Client ID and Client secret. 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 smallinvoice connector, then ask in plain words. The AI picks the tools.
| Tool | Type | What it does |
|---|---|---|
smallinvoice_get_owner | read | Get the account owner The smallinvoice account the API client belongs to (the owner's id and details). A cheap check that the connection works. GET /auth/owner. |
smallinvoice_list_contacts | read | List contacts List contacts (customers and suppliers): name, type (company or person), relation, e-mail, currency. Add with=main_address for the address. Needs the "contact" scope. GET /contacts. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_get_contact | read | Get a contact One contact by id, with its fields. Add with=main_address for the main address. Needs the "contact" scope. GET /contacts/{id}. |
smallinvoice_list_contact_addresses | read | List a contact's addresses All addresses of one contact. Needs the "contact" scope. GET /contacts/{contactId}/addresses. |
smallinvoice_list_contact_people | read | List a contact's people The contact persons of one company contact. Needs the "contact" scope. GET /contacts/{contactId}/people. |
smallinvoice_list_contact_groups | read | List contact groups List the contact groups. Needs the "contact" scope. GET /contacts/configuration/groups. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_list_invoices | read | List invoices List invoices: number, contact, dates, total, currency, status. Filter by contact_id or a JSON filter. Needs the "invoice" scope. GET /receivables/invoices. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_get_invoice | read | Get an invoice One invoice by id with its positions, totals and status. Needs the "invoice" scope. GET /receivables/invoices/{id}. |
smallinvoice_list_invoice_payments | read | List payments of an invoice The payments recorded on one invoice. Needs the "invoice" scope. GET /receivables/invoices/{invoiceId}/payments. |
smallinvoice_list_offers | read | List offers List offers (quotes). Filter by contact_id or a JSON filter. Needs the "offer" scope. GET /receivables/offers. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_get_offer | read | Get an offer One offer (quote) by id with its positions and totals. Needs the "offer" scope. GET /receivables/offers/{id}. |
smallinvoice_list_order_confirmations | read | List order confirmations List order confirmations. Filter by contact_id or a JSON filter. Needs the "order_confirmation" scope. GET /receivables/order-confirmations. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_get_order_confirmation | read | Get an order confirmation One order confirmation by id. Needs the "order_confirmation" scope. GET /receivables/order-confirmations/{id}. |
smallinvoice_list_delivery_notes | read | List delivery notes List delivery notes. Filter by contact_id or a JSON filter. Needs the "delivery_note" scope. GET /receivables/delivery-notes. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_get_delivery_note | read | Get a delivery note One delivery note by id. Needs the "delivery_note" scope. GET /receivables/delivery-notes/{id}. |
smallinvoice_list_products | read | List catalog products List the catalog's products (articles). Needs the "catalog" scope. GET /catalog/products. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_list_services | read | List catalog services List the catalog's services. Needs the "catalog" scope. GET /catalog/services. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_list_units | read | List units List the units (piece, hour, ...) with their ids, which an invoice position's unit_id refers to. Needs the "configuration" scope. GET /catalog/configuration/units. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_list_bank_accounts | read | List bank accounts List the account's bank accounts (as printed on documents). Needs the "configuration" scope. GET /configuration/bank-accounts. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_list_projects | read | List projects List projects. Needs the "project" scope. GET /reporting/projects. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_get_project | read | Get a project One project by id. Needs the "project" scope. GET /reporting/projects/{id}. |
smallinvoice_list_working_hours | read | List working hours List recorded working hours (time tracking entries). Needs the "working_hours" scope. GET /reporting/working-hours. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_list_efforts | read | List efforts List efforts (expenses and services recorded against projects). Needs the "effort" scope. GET /reporting/efforts. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_list_activities | read | List activities List activities (the kinds of work that hours are booked on). Needs the "activity" scope. GET /reporting/activities. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_list_cost_units | read | List cost units List cost units. Needs the "cost_unit" scope. GET /reporting/cost-units. Returns count, total, next_offset (pass it as offset for the next page) and the items. |
smallinvoice_create_contact | write | Create a contact WRITE: creates a new company contact (customer) in smallinvoice, with its main address. Needs the "contact" scope. POST /contacts. Nothing is sent to anyone. Private persons are not supported here (smallinvoice needs more fields for them): create those in smallinvoice. Check smallinvoice_list_contacts first so you do not create a duplicate. |
smallinvoice_create_invoice | write | Create an invoice WRITE: creates a new invoice for a contact. Needs the "invoice" scope. POST /receivables/invoices. It is only created: it is NOT sent by e-mail or post and its status is not changed; the user reviews it in smallinvoice. Not idempotent: calling it twice creates two invoices. Use smallinvoice_list_contacts / smallinvoice_list_units first for the ids. |
smallinvoice_usage_status | Usage status (free-tier meter) Report the caller's current usage: the plan, calls used this month, the limit of the plan (the free monthly cap or the Pro fair use limit), remaining, and whether the limit is reached. Read-only; does not count against the meter. | |
smallinvoice_request_feature | Request a missing feature Tell usefulapi that the user needs something the smallinvoice 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. | |
smallinvoice_upgrade | Upgrade to Pro (unlimited*) Get Pro: unlimited tool calls (fair use limit: 10,000 a month) on smallinvoice (the free tier caps monthly usage). Plans: "monthly" — $9/month; "yearly" — $90/year (2 months free). Cancel any time: Pro then runs to the end of the paid period, so it also suits a one-time job. *A fair use limit applies. For heavy use (near Pro's limit): "plus" or "plus_yearly" — Pro+, $39/month or $390/year, unlimited tool calls (fair use limit: 100,000 a month); an existing Pro subscription changes to Pro+ in place (needs confirm: true; the price difference for the rest of the period is charged at once). Otherwise returns a short link to open in your browser (it opens Stripe Checkout); after payment the account upgrades automatically. Does not count against the meter. | |
smallinvoice_cancel_subscription | Cancel the Pro subscription Cancel the caller's smallinvoice Pro subscription at the end of the paid period (no refund for the current period; Pro continues until then, then the free tier applies). Requires confirm: true. Run smallinvoice_upgrade later to undo the cancel before the period ends. Does not count against the meter. |
| Plan | Price | Limit |
|---|---|---|
| Free | $0 | 50 tool calls / month |
| Proper account | $9/mo · $90/yr | Unlimited* |
*Pro fair use limit: 10,000 tool calls a month on this server. For more, write to [email protected].
Pro covers this smallinvoice server only. Subscribe with smallinvoice_upgrade (it returns a Stripe Checkout link). Cancel any time with smallinvoice_cancel_subscription: Pro continues to the end of the paid period, with no refund for the current period, and running smallinvoice_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 smallinvoice. The server calls the smallinvoice API with your own smallinvoice access, so it sees only the data that your account can see.
Yes. In Claude, add this server's URL as a custom connector. In ChatGPT, add it as a custom MCP server in Plugins. Then log in once. Cursor, VS Code, Claude Code and Codex work too. See the setup steps.
The login page asks for your Client ID and Client secret. See Before you connect for where to find them.
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 Client ID and Client secret. 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 smallinvoice 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 smallinvoice.
Yes, if you approve it. 2 of the 27 smallinvoice tools can create or change data. The other 25 are marked read-only. Most MCP clients ask you to approve a tool call before it runs.
The Free plan gives 50 tool calls / month. Pro costs $9/mo or $90/yr, with unlimited tool calls (fair use limit: 10,000 tool calls a month), for this smallinvoice server only. Cancel any time: Pro then runs to the end of the paid period. Run smallinvoice_usage_status to see how many calls you used.
Ask the AI to run smallinvoice_upgrade: it returns a Stripe Checkout link. To cancel, run smallinvoice_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 smallinvoice_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, ChatGPT, Codex, 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.