FastBill MCP
Read and create FastBill invoices, customers, estimates, expenses and time entries
Connect to FastBill accounting software to view customers, invoices, estimates, expenses and time entries. Create invoices, customers, projects and time entries. Requires FastBill account and API credentials.
Try asking Muse: "Show me all unpaid invoices from this month and mark the one from Acme Corp as paid"
See the most upvoted connectors
Source: Found in the official MCP Registry (io.usefulapi/fastbill) · First listed October 28, 2026
Last 24 hours
Each bar is one check, every 15 minutes. Green means it answered. Last checked 26 min ago.
Is it safe to connect?
What Muse can see: It does not ask you to sign in, so it cannot see your accounts. It only sees what Muse sends it from your request.
Before it acts: Read what Muse plans to do before you approve it, and remove the app from Muse when you stop using it.
musedirectory.ai is not part of Meta. More about how Muse handles your information
How to add it to Muse
Not in Muse's Connectors list yet, but Muse can still use it. Copy the request below and paste it into Muse. Muse asks before it shares anything with the app's site. Meta does not review apps used this way, so only use ones you trust. We tested this in the Muse app on September 24, 2026: Muse used an app's link directly this way and returned a live answer.
https://fastbill.usefulapi.io/mcpNot in Muse's Connectors list yet. Muse can still use it: its page gives you a request to paste into Muse.
Also use it in ChatGPT or Claude
FastBill MCP is a remote MCP server, so any assistant that can add a custom connector by link can use it. Same link, same tools.
Add it to ChatGPT
- 1
Open ChatGPT settings
In ChatGPT, open Settings, then Connectors (called Apps & Connectors on some accounts).
- 2
Turn on developer mode
Under Advanced settings, switch on Developer mode. That is what lets you add a connector by link.
- 3
Create the connector
Choose Create, give it a name, paste the link as the MCP server URL, and save. If it needs a sign-in, ChatGPT asks for it here.
- 4
Use it in a chat
Start a chat, open the tools menu, pick the connector, and ask. ChatGPT asks before it runs a tool the first time.
Custom connectors need a paid ChatGPT plan, and on Team, Enterprise and Edu accounts only an admin can add them. Our "Working" label means the server answered us; it cannot tell whether your plan lets you add it. All connectors that work in ChatGPT
Add it to Claude
- 1
Open Claude settings
In Claude, open Settings, then Connectors.
- 2
Add a custom connector
Choose Add custom connector, give it a name, and paste the link.
- 3
Connect and use it
If it needs a sign-in, Claude sends you to it. Then turn the connector on in a chat from the tools menu and ask.
Custom connectors are available on paid Claude plans; on Team and Enterprise accounts an admin may need to add them. Our "Working" label means the server answered us; it cannot tell whether your plan lets you add it. All connectors that work in Claude
https://fastbill.usefulapi.io/mcpWhat people ask Muse to do
Technical details: safety screening, tools, response time and recent checks
Response time at the last check: 1368ms. Worked in 100% of checks over 30 days.
Screening · October 29, 2026
Screened, no issues found
Screening looks for known threats and hidden instructions at the time of the check, and runs again weekly and whenever the tool list changes. It cannot see the server's code, so only connect what you need and review what Muse asks to do. How screening works.
Tools · 22
fastbill_list_customersList customers (name, address, e-mail, VAT id, payment terms and bank details as stored in FastBill). Filter by search term (organization, name, address, zip, e-mail or tags), customer number, country or city. customer.get.fastbill_get_customerOne customer by FastBill customer id. customer.get with CUSTOMER_ID.fastbill_list_contactsList contact persons of customers (name, position, e-mail, phone). Filter by customer, search term or contact id. contact.get.fastbill_list_invoicesList outgoing invoices, drafts and credit notes with totals, state (draft, unpaid, overdue, paid, canceled), dates and line items. Filter by customer, number, type, date ranges (invoice date, due date, paid date, last update). invoice.get.fastbill_get_invoiceOne invoice by FastBill invoice id, with all line items, VAT, payments and the document URL. invoice.get with INVOICE_ID.fastbill_list_recurring_invoicesList recurring invoice templates (customer, interval data, totals, items). recurring.get.fastbill_list_estimatesList estimates (quotes) with state (a created, b sent, c negotiation, d accepted, e rejected, f invoiced), totals and items. estimate.get.fastbill_list_expensesList expense entries (supplier, category, net/VAT/gross, dates, document URL). Filter by invoice number or date ranges. expense.get.fastbill_list_revenuesList revenue entries (income booked in FastBill: customer, totals, dates, payments). Takes the same filters as invoices. revenue.get.fastbill_list_articlesList products and services (article number, type, title, unit price, VAT, unit). article.get.fastbill_list_projectsList projects (name, customer, hourly rate, VAT, start/end date). project.get.fastbill_list_time_entriesList work time entries (customer, project, date, minutes, billable minutes, comment, invoice). Without filters FastBill returns the latest entries of the current month. time.get.fastbill_list_templatesList the invoice/estimate templates (template id, name, hash). Use a template id with the create tools. Ids change whenever a template is edited. template.get.fastbill_create_customerWRITE: create a customer. customer_type is required; a business needs organization, a consumer needs last_name. Bank details are not accepted by this tool. FastBill does not check for duplicates, so search with fastbill_list_customers first. customer.create.fastbill_update_customerWRITE: update fields of an existing customer; only the fields you pass change. Bank details are not accepted by this tool. customer.update.fastbill_create_invoiceWRITE: create an invoice for a customer from line items. FastBill stores it as a draft; it gets its number and becomes final only with fastbill_complete_invoice, and it is never sent by this tool. Check the result with fastbill_get_invoice. invoice.create.fastbill_complete_invoiceWRITE, NOT REVERSIBLE: turn a draft invoice into a final invoice. FastBill assigns the invoice number and PDF; a final invoice can no longer be edited (it can only be canceled in FastBill). Nothing is sent to the customer. Only call this after the user confirmed the draft. invoicfastbill_set_invoice_paidWRITE: mark a final invoice as paid, with the payment date and method. invoice.setpaid.fastbill_create_estimateWRITE: create an estimate (quote) for a customer from line items. It is not sent. estimate.create.fastbill_create_articleWRITE: create a product or service (article number, title and unit price are required). article.create.fastbill_create_projectWRITE: create a project for a customer (name and customer are required). project.create.fastbill_create_time_entryWRITE: book a work time entry on a project (customer, project and start time are required). time.create.Recent checks
Link
https://fastbill.usefulapi.io/mcpQuestions about FastBill MCP in Muse
How do I connect FastBill MCP to Muse?
Not in Muse's Connectors list yet, but Muse can still use it. Paste this into Muse: "Use FastBill MCP to help me. It is a free service with an MCP server at https://fastbill.usefulapi.io/mcp. It does not need an API key. Ask me before you share anything with it." Muse asks before it shares anything with the app's site. Meta does not review apps used this way, so only use ones you trust. We tested this in the Muse app on September 24, 2026: Muse used an app's link directly this way and returned a live answer.
Is FastBill MCP working right now?
At the last check (October 29, 2026, 11:31 UTC) the endpoint was working, answering in 1368ms. Over the last 7 days it answered 100% of health checks. It is checked every 15 minutes.
Is FastBill MCP safe to connect to Muse?
It was screened on October 29, 2026 with the result "screened, no issues found". Screening checks the domain against threat feeds and reads the tools for hidden instructions and requests for passwords or card numbers. It cannot see the server's code, so grant only the access you need.
What can FastBill MCP do in Muse?
It exposes 22 tools, including fastbill_list_customers, fastbill_get_customer, fastbill_list_contacts, fastbill_list_invoices. For example, you could ask Muse: "Show me all unpaid invoices from this month and mark the one from Acme Corp as paid"
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