Poland's e-invoicing (KSeF) via AI: issue an invoice by talking to Claude
KSeF, Poland's national e-invoicing system, is becoming mandatory, and integrating with its API costs time. This is an open MCP server for KSeF: you ask Claude to issue an invoice and it creates, checks and sends it to KSeF.
Industry: Accounting, businesses, integrators
In short
- An open MCP server for KSeF, source on GitHub
- 32 tools: login, issue, validate, download
- Works in Claude Desktop, Claude Code and ChatGPT
- KSeF API v2, FA(3) format, online and batch sessions
About the project
KSeF, Poland's national e-invoicing system, is becoming mandatory. Businesses must issue invoices through its API, which means integration, tokens, an XML format and sessions. For many that is a wall.
The challenge
Issuing an invoice to KSeF had to become as simple as writing a sentence. Instead of writing an integration, you ask the AI and it talks to KSeF for you.
Goals
- Hide the complexity of the KSeF API behind a simple chat
- Cover the full flow: login, issue, validate, download
- Stick to the official FA(3) format and API v2
- Do it safely: token, JWT and encrypted sending
Technical challenges
KSeF sessions and tokens
KSeF needs token authentication, an online or batch session and JWT. The server handles this underneath so the user never touches it.
FA(3) compliance
The invoice must match the FA(3) schema or KSeF rejects it. Validation before sending was added to catch errors early.
Encrypted sending
Invoice sending is encrypted and the token is not logged anywhere.
Solution and implementation
You ask, the AI issues
You ask for an invoice in plain language. Claude creates a draft, validates it against FA(3) and sends it to KSeF, and you get the KSeF number and confirmation.
The full flow, not just sending
Searching invoices, downloading XML, processing status, batch handling and tokens. Thirty tools cover real KSeF work.
Results
Integration without integration
Instead of weeks of coding against the KSeF API, you issue an invoice with a sentence in Claude.
Ready for the mandate
A business or accounting office has the tool in time for when KSeF becomes mandatory.
Takeaways
MCP removes the integration wall
Instead of learning every API, you give the AI tools and speak plainly. That shortens the path from idea to working.
Scope
- KSeF authentication
- Issuing e-invoices
- FA(3) validation
- Download and status
Technologies
- MCP
- KSeF API v2
- Node.js
- FA(3)
Frequently asked questions
What is this MCP server for KSeF?
A tool that connects KSeF to AI. You ask Claude or ChatGPT to issue an invoice and the server talks to KSeF for you.
Does it work with mandatory KSeF?
Yes. It is based on KSeF API v2 and the FA(3) format, which is what applies to issuing e-invoices.
Do I need to code?
Not to issue invoices. You connect the server once and issue invoices with a plain sentence in Claude.
Is it safe?
Authentication uses a token and JWT, and invoice sending is encrypted. The token is not logged anywhere.
Where is the code?
The server is public on GitHub and available as an npm package, so you can review it and run it yourself.