billy-mcp

An MCP server for billy.dk — Danish accounting, controllable from Claude (or any MCP-compatible AI client) over the official Billy v2 REST API.

Read your invoices, categorise bank lines, draft new invoices from notes, upload receipt PDFs and attach them to bills, run a P&L on demand, prep MOMS reports, browse the audit log. 65 tools covering the full Billy v2 surface. Write operations are gated behind an explicit confirm: true so the AI cannot post to your books without per-call acknowledgement.

• Language: TypeScript, Node 20+

• Auth: personal access token (X-Access-Token header, no OAuth dance)

• Transport: stdio MCP, install once in your client's config

• License: MIT — use freely, including commercially

• Status: v0.3.0, in production use on a real Danish ApS

Why this exists

Dinero (one of the two major Danish accounting platforms) gates developer API access behind a partner approval process that's effectively closed to solo founders and small studios. Billy's API is open: a personal access token, well-documented endpoints, no gatekeeping. This MCP wraps it.

If you run a Danish ApS or sole proprietorship on Billy and you're tired of clicking through the UI for routine bookkeeping, this gives you natural-language control over the entire account, with a built-in safety pattern so the AI can't quietly mess up your books.

Related MCP server: Fortnox MCP Server

Install in 30 seconds (non-technical path)

If you're using Claude Code (or any AI client with shell + filesystem access), copy this prompt into your client and let the agent install everything for you:

Install the billy-mcp from https://github.com/cimalys/billy-mcp into my Claude config so I can manage my billy.dk accounting through chat.

Steps:

1. Clone https://github.com/cimalys/billy-mcp to ~/billy-mcp

2. Run cd ~/billy-mcp && npm install && npm run build

3. Ask me for my Billy API token (I'll get it from billy.dk → Settings → Access tokens → Create new). Save it to ~/billy-mcp/.env as BILLY_API_TOKEN=...

4. Add the MCP to my user-scope Claude config: claude mcp add --scope user --transport stdio billy --env BILLY_API_TOKEN=<token> -- node ~/billy-mcp/dist/index.js

5. Confirm with claude mcp list — billy should show as Connected.

When done, run billy_whoami to verify everything works.

The AI handles the cloning, building, token prompting, config edit, and verification. You just paste your token when asked. Total time: under 2 minutes.

Install (technical path)

# 1. Clone
git clone https://github.com/cimalys/billy-mcp.git ~/billy-mcp
cd ~/billy-mcp

# 2. Build
npm install
npm run build

# 3. Get your Billy access token
#    billy.dk → Settings → Access tokens → Create new
#    Tokens do not expire.
echo "BILLY_API_TOKEN=your_token_here" > .env

# 4. Smoke-test the token against the live Billy API
npm run smoke
# Expected: prints your org, three unmatched bank lines, three draft invoices.

# 5. Wire into Claude Code
TOKEN=$(awk -F= '/^BILLY_API_TOKEN=/{sub(/^BILLY_API_TOKEN=/,"",$0); print}' .env | tr -d '\r\n "')
claude mcp add --scope user --transport stdio billy \
  --env "BILLY_API_TOKEN=$TOKEN" \
  -- node "$PWD/dist/index.js"

# 6. Verify
claude mcp list | grep billy   # → "billy: node ... ✔ Connected"

Restart your Claude session. The billy tools become available immediately.

How it's safe — the write-guard

Every mutating tool refuses to execute without confirm: true. Without confirm, the tool returns a dry-run preview of the API call it would have made.

Example — without confirm

{
  "tool": "billy_create_invoice",
  "input": { "invoice": { "contactId": "abc", "entryDate": "2026-06-14", ... } }
}

Returns:

[DRY RUN — write blocked]

Action: create invoice

Payload that would be sent to Billy:
{
  "invoice": { "contactId": "abc", "entryDate": "2026-06-14", ... }
}

To execute, re-issue the same tool call with the additional field: "confirm": true
(This is a hard guardrail in the MCP — no Billy write happens until you explicitly confirm.)

Example — with confirm

{
  "tool": "billy_create_invoice",
  "input": { "invoice": { ... }, "confirm": true }
}

Now the call hits Billy, returns the created invoice, and logs to stderr:

[billy-mcp 2026-06-14T09:25:00Z] WRITE confirmed → create invoice

This means an AI client can never autonomously write to your books in a single turn. It can suggest, preview, and explain — but the actual mutation requires you (or the LLM, with your visible agreement) to issue a second call with confirm.

Read tools are not gated. Listing, getting, reports, audit log, reference data — all fire immediately. The guardrail protects only state changes.

Tool catalog (65 tools)

Organisation

• billy_whoami — current org details (read-only)

• billy_update_organization — update fields like VAT no, payment terms, address (write-guarded)

Invoices

• billy_list_invoices, billy_get_invoice — read

• billy_create_invoice, billy_update_invoice, billy_delete_invoice — write-guarded

• billy_approve_invoice — draft → approved (write-guarded)

• billy_send_invoice — send by email via Billy (write-guarded)

Bills (expenses / supplier invoices)

• billy_list_bills, billy_get_bill — read

• billy_create_bill, billy_update_bill, billy_delete_bill, billy_approve_bill — write-guarded

Contacts & contact persons

• billy_list_contacts, billy_get_contact, billy_list_contact_persons — read

• billy_create_contact, billy_update_contact, billy_delete_contact, billy_create_contact_person — write-guarded

Products

• billy_list_products, billy_get_product — read

• billy_create_product, billy_update_product, billy_delete_product — write-guarded

Chart of accounts

• billy_list_accounts, billy_get_account, billy_list_account_groups — read

• billy_create_account, billy_update_account — write-guarded

Bank accounts, payments, lines (reconciliation)

• billy_get_bank_account, billy_list_bank_payments, billy_list_bank_lines, billy_get_bank_line — read

• billy_create_bank_account, billy_create_bank_payment, billy_match_bank_line, billy_unmatch_bank_line — write-guarded

Daybook (manual journal entries)

• billy_list_daybooks, billy_list_daybook_transactions — read

• billy_create_daybook_transaction — write-guarded

Tax (MOMS / VAT)

• billy_list_tax_rates, billy_list_tax_rulesets, billy_list_sales_tax_returns, billy_get_sales_tax_return — read

Reports

• billy_report_profit_loss — P&L for a date range

• billy_report_balance — balance sheet at a point in time

• billy_report_sales_tax — MOMS report

• billy_report_invoiced_sales — invoiced sales by contact/product

Postings & audit

• billy_list_postings — underlying ledger entries

• billy_list_action_stream — recent activity log

Webhooks

• billy_list_webhooks — read

• billy_create_webhook, billy_delete_webhook — write-guarded

Reference data (all read-only)

• billy_list_currencies, billy_list_countries, billy_list_payment_terms_modes, billy_list_units

Files / attachments

• billy_list_files, billy_get_file — read

• billy_upload_file — upload a local PDF/JPG/PNG/GIF to Billy; returns id (write-guarded; other extensions rejected — Billy v2 limitation)

• billy_attach_file_to_bill, billy_attach_file_to_invoice — write-guarded

Example prompts after install

"Run billy_whoami and tell me my org details."

"Show me my outstanding invoices and total revenue."

"List unmatched bank lines from the last 30 days and propose a category for each."

"Draft an invoice to Acme ApS for 45,000 DKK for the AI Readiness Audit,
payment terms net 14. Show me the dry run first."

"Generate a P&L for 2026-06-01 to 2026-06-13."

"What was my biggest expense category this month?"

"Set my organisation's payment terms to net 14 days. Preview first."

"Upload /Users/me/Downloads/aws-jun.pdf to Billy, create a bill for AWS
240 EUR for cloud infrastructure, and attach the file. Preview each
step before confirming."

Billy v2 API quirks this MCP works around

Three behaviours that aren't obvious from Billy's docs, patched in this MCP so you don't have to learn them the hard way:

1. PUT /v2/organization returns 405 — the singular endpoint is GET-only. Org updates have to go to the plural endpoint with the org id: PUT /v2/organizations/<id>. billy_update_organization resolves the id from whoami first, then hits the right endpoint.

2. GET /v2/bankAccounts returns 405 — Billy v2 doesn't let you list bank accounts. Single lookup by id works (billy_get_bank_account). For the default invoice bank account id, read it from billy_whoami → organization.defaultInvoiceBankAccountId.

3. GET /v2/bankLines requires accountId — the API rejects unfiltered list calls. The MCP marks accountId as required and points you at whoami for the default.

4. GET /v2/paymentMethods returns 404 — the resource doesn't actually exist on Billy v2, despite appearing in some references. Tool removed in 0.3.0.

5. /v2/files is append-only. No DELETE (single or bulk), no PUT — files uploaded via the API cannot be removed or modified via the API. Cleanup must happen through the Billy web UI. No file-delete tool is included in this MCP because Billy doesn't expose one.

6. /v2/files only accepts pdf, jpg, jpeg, png, gif. Any other extension returns a generic 422. billy_upload_file validates up-front (0.3.2+) so callers get a clean error message instead.

Limitations & non-goals

• Not a substitute for a Danish revisor. Bogføringsloven 2022 puts the responsibility for accurate bookkeeping on company management. This MCP makes the AI a useful assistant; it does not replace professional accounting signoff.

• No autonomous loop. This is deliberately a single-tool-call MCP. If you want an agent that polls bank lines nightly and auto-categorises them, that's a separate layer you'd build on top.

• Personal-token auth only. OAuth flow not implemented (no need for a single-user setup; would be needed for SaaS multi-tenant).

• File upload requires a local path. billy_upload_file reads from a path on the same machine the MCP runs on. To ingest a receipt that lives only in your email, either save it to disk first or forward it to your Billy bill-capture address (organization.billEmailAddress from whoami) — Billy auto-creates a draft bill.

Contributing

Issues and PRs welcome. Particular interest in:

• File upload tool (multipart POST /v2/files)

• Webhook receiver pattern for real-time reconciliation

• Coverage of the umbrellaUsers and apps endpoints (multi-org)

• Equivalent MCPs for Dinero once their API opens up

Author

Maintained by Cimalys ApS — Copenhagen.

If you'd like a Billy MCP deployed for your firm, a custom integration with other Danish business systems, or general AI implementation work, get in touch at nlej@cimalys.com.