Spec Driven Development
MCP Server that facilitates spec-driven development workflows, not just Vibe Coding.
Description from the maker (original English)
Read FastBill customers, invoices, estimates, expenses; create customers, invoices, projects.
These three are never merged into one score: opinions, measurements and popularity are different things.
We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.
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Works in Claude on the web, desktop and mobile:
https://fastbill.usefulapi.io/mcpRun this in your terminal
claude mcp add --transport http fastbill https://fastbill.usefulapi.io/mcpPaste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json
{
"mcpServers": {
"fastbill": {
"url": "https://fastbill.usefulapi.io/mcp"
}
}
}Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.
Paste into .vscode/mcp.json in your project
{
"servers": {
"fastbill": {
"type": "http",
"url": "https://fastbill.usefulapi.io/mcp"
}
}
}Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.
ChatGPT connects only to servers on the internet:
https://fastbill.usefulapi.io/mcpMenu names can differ slightly by plan and over time.
Your choice stays on this device in a cookie; no account needed.
These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.
Tool names and descriptions exactly as the server reported them on Nov 6, 2026. The maker wrote them, not us; we show them as plain text.
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. invoic
fastbill_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.
We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 6, 2026
The registry name was verified against the domain usefulapi.io (the registry checks domain ownership)
We have not read this repo from GitHub yet
We have not read this repo from GitHub yet
Responded in 66 ms (HTTP 200)
No sign-in needed
Read 22 tool descriptions and found no hidden instructions to the AI
Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.
It passed 3 of 3 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.
The registry does not list a required key, though some servers ask you to sign in on first use.
It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.
The GitHub repo last changed –, and the latest version (1.11.3) reached the registry yesterday.
Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT in developer mode.
In the same category: Spec Driven Development, Remote Desktop Commander, debuff
Servers in the same category from other makers, sorted by stars.
Reading a card:★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi
MCP Server that facilitates spec-driven development workflows, not just Vibe Coding.
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Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.
Live endpoint: https://fastbill.usefulapi.io/mcp
https://fastbill.usefulapi.io/mcp.claude mcp add --transport http fastbill https://fastbill.usefulapi.io/mcp, then run /mcp to log in.{
"mcpServers": { "fastbill": { "url": "https://fastbill.usefulapi.io/mcp" } } }
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, and the login page asks for your FastBill credentials.
Step-by-step setup, where to find your credentials, and FAQ: https://usefulapi.io/fastbill/
On first connect you will paste your FastBill login e-mail and API key. They are validated, stored per-user, and scoped to you. No keys in config files.
| Tool | Type | What it does |
|---|---|---|
fastbill_list_customers | read | List customers |
fastbill_get_customer | read | Get customer |
fastbill_list_contacts | read | List contacts |
fastbill_list_invoices | read | List invoices |
fastbill_get_invoice | read | Get invoice |
fastbill_list_recurring_invoices | read | List recurring invoices |
fastbill_list_estimates | read | List estimates |
fastbill_list_expenses | read | List expenses |
fastbill_list_revenues | read | List revenues |
fastbill_list_articles | read | List products |
fastbill_list_projects | read | List projects |
fastbill_list_time_entries | read | List time entries |
fastbill_list_templates | read | List document templates |
fastbill_create_customer | write | Create customer |
fastbill_update_customer | write | Update customer |
fastbill_create_invoice | write | Create invoice |
fastbill_complete_invoice | write | Finalize invoice |
fastbill_set_invoice_paid | write | Mark invoice paid |
fastbill_create_estimate | write | Create estimate |
fastbill_create_article | write | Create product |
fastbill_create_project | write | Create project |
fastbill_create_time_entry | write | Create time entry |
fastbill_usage_status | meta | Usage status (free-tier meter) |
fastbill_request_feature | meta | Request a missing feature |
fastbill_upgrade | meta | Upgrade to Pro or Pro+ |
fastbill_cancel_subscription | meta | Cancel the Pro subscription |
read tools are read-only; write tools mutate data (clients should confirm them); meta tools report usage, manage your subscription or send a feature request.
| Plan | Price | Limit |
|---|---|---|
| Free | $0 | 50 tool calls / month |
| Pro (per account) | $9/mo or $90/yr (2 months free) | Unlimited* |
\*Pro has a fair use limit of 10,000 tool calls a month on this server. For more, write to support@usefulapi.io.
Pro covers this server only. Subscribe with fastbill_upgrade (it returns a Stripe Checkout link). Cancel any time with fastbill_cancel_subscription: Pro continues to the end of the paid period, with no refund for the current period, and running fastbill_upgrade before then undoes the cancel. Or write to support@usefulapi.io.
MIT