easybill MCP Server

An MCP server for the easybill REST API. Gives any MCP-capable assistant — Claude Code, Claude Desktop, Cursor, VS Code, Windsurf, Zed, Codex CLI, Gemini CLI, Cline — access to your invoices, customers, article catalogue, payments, projects and tracked time.

Built on the official @modelcontextprotocol/sdk (TypeScript), talking stdio.

• 54 tools across 12 easybill resources

• Read-only by default — create/update/delete tools stay unregistered unless you opt in

• Workflow-aware — ships server instructions so the agent resolves the customer before writing a document, instead of guessing where to start

• Fuzzy customer search the easybill API itself does not offer

• Self-throttling to respect easybill's 10–60 requests/minute cap

• Context-aware responses — compact field sets, pagination metadata, automatic truncation

Setup

1. Get an easybill API key

In easybill: Einstellungen → App-Center → API. Create a key and copy it.

2. Register it with your client

This is a plain stdio MCP server published on npm, so any MCP client can run it with npx — no clone, no build, no global install:

npx -y easybill-mcp

Configuration is entirely through environment variables (full list under Configuration). Two matter now:

• Leave EASYBILL_ENABLE_WRITES unset to start read-only.

• Set EASYBILL_RATE_LIMIT_PER_MINUTE to 10 on easybill's PLUS plan or 60 on BUSINESS.

Most clients use the same JSON shape under an mcpServers key:

{
  "mcpServers": {
    "easybill": {
      "command": "npx",
      "args": ["-y", "easybill-mcp"],
      "env": {
        "EASYBILL_API_KEY": "your_api_key_here",
        "EASYBILL_RATE_LIMIT_PER_MINUTE": "10"
      }
    }
  }
}

Where that block goes:

Windows: if a client fails to start npx, use "command": "cmd" with "args": ["/c", "npx", "-y", "easybill-mcp"].

Claude Code

claude mcp add easybill \
  --env EASYBILL_API_KEY=your_api_key_here \
  --env EASYBILL_RATE_LIMIT_PER_MINUTE=10 \
  -- npx -y easybill-mcp

claude mcp add does not overwrite an existing entry — to change the environment later, claude mcp remove easybill -s local first, then add it again.

VS Code (GitHub Copilot agent mode)

VS Code uses servers, not mcpServers, and can prompt for the key instead of storing it in the file. Put this in .vscode/mcp.json (workspace) or open MCP: Open User Configuration:

{
  "inputs": [
    { "id": "easybill_key", "type": "promptString", "description": "easybill API key", "password": true }
  ],
  "servers": {
    "easybill": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "easybill-mcp"],
      "env": {
        "EASYBILL_API_KEY": "${input:easybill_key}",
        "EASYBILL_RATE_LIMIT_PER_MINUTE": "10"
      }
    }
  }
}

Zed

In settings.json:

{
  "context_servers": {
    "easybill": {
      "source": "custom",
      "command": "npx",
      "args": ["-y", "easybill-mcp"],
      "env": {
        "EASYBILL_API_KEY": "your_api_key_here",
        "EASYBILL_RATE_LIMIT_PER_MINUTE": "10"
      }
    }
  }
}

Codex CLI

In ~/.codex/config.toml:

[mcp_servers.easybill]
command = "npx"
args = ["-y", "easybill-mcp"]
env = { EASYBILL_API_KEY = "your_api_key_here", EASYBILL_RATE_LIMIT_PER_MINUTE = "10" }

Hosted clients that only speak remote MCP

Some clients (ChatGPT connectors, hosted agent platforms) accept only HTTP/SSE endpoints, not stdio. Bridge it locally:

npx -y supergateway --stdio "npx -y easybill-mcp"

Only do this if you understand the exposure: anything that reaches that endpoint reaches your accounting data. Keep it bound to localhost or behind a tunnel with authentication, and never run the bridge with writes enabled unless the endpoint is protected.

3. Verify the connection

Ask the assistant to call easybill_get_server_info. It reports the mode, the limits and whether easybill accepted the credentials:

{
  "server_version": "1.0.1",
  "writes_enabled": false,
  "tools_registered": { "read_only": 28, "write": 0, "withheld_because_writes_disabled": 26 },
  "rate_limit_per_minute": 10,
  "connection": "ok — credentials accepted by easybill"
}

4. Enable writes, once you trust it

Add EASYBILL_ENABLE_WRITES=true to the server's environment:

claude mcp add easybill \
  --env EASYBILL_API_KEY=your_api_key_here \
  --env EASYBILL_RATE_LIMIT_PER_MINUTE=10 \
  --env EASYBILL_ENABLE_WRITES=true \
  -- npx -y easybill-mcp

The 26 write tools are registered at startup, so the change only takes effect once the client restarts the server process — editing the config in a running session is not enough. Confirm with easybill_get_server_info: writes_enabled must read true.

Related MCP server: datagate-mcp

Running from a local clone

For development, or to run a version you have not published:

git clone https://github.com/stack74/easybill-mcp.git
cd easybill-mcp
npm install
npm run build

Then point the client at the built entry point instead of npx — "command": "node", "args": ["/absolute/path/to/easybill-mcp/dist/index.js"], same env block. Or straight from GitHub without cloning, which is slower because it compiles TypeScript on install via the prepare script and needs a toolchain:

npx -y github:stack74/easybill-mcp

Test locally first

Copy .env.example to .env, put your key in it, then run the read-only self-test:

cp .env.example .env
$EDITOR .env
npm run smoke

It makes five read-only calls and prints what came back:

easybill-mcp-server v1.x.y self-test
API: https://api.easybill.de/rest/v1
Throttle: 60 req/min | writes disabled

  OK    Auth check (customer groups): total=2  first=Stammkunden
  OK    Customers: total=42  first=Example GmbH
  OK    Invoices: total=128  first=RE-2026-0001
  OK    Unpaid invoices: total=7  first=RE-2026-0117
  OK    Articles (positions): total=95  first=ART-001

All probes passed. The server is ready to register with an MCP client.

(Numbers above are illustrative — you will see your own account's totals.)

On a bad key it fails on the first call and stops, so it never burns your rate limit.

To poke at individual tools interactively:

npm run inspect     # MCP Inspector, loads .env

Note: .env is only read by these npm scripts, via Node's --env-file. The server itself reads plain environment variables — when you register it with an MCP client, pass the key through the client's config, not via .env.

Publishing to npm

npm login                  # once, needs an npmjs.com account
npm run build && npm run smoke
npm publish                # unscoped packages are public by default

Verify what ships before you publish — npm pack --dry-run lists the tarball contents. Only dist/, README.md, LICENSE and package.json are included; src/ and .env are not.

For later releases bump the version first (npm version patch|minor|major), which also creates a git tag. npm does not allow republishing an existing version.

Configuration

Tools

Customer lookup

The easybill API has no full-text search, so this tool tries exact filters first, then pages the customer list and scores candidates locally. It tolerates legal forms (GmbH & Co. KG), punctuation (M.B. MUSTERMANN vs MB Mustermann), umlauts and word order.

Documents — invoices, offers, credit notes, deliveries, orders

Customers, contacts, groups

easybill_list_customers, easybill_get_customer, easybill_create_customer, easybill_update_customer, easybill_delete_customer, easybill_list_contacts, easybill_get_contact, easybill_create_contact, easybill_update_contact, easybill_delete_contact, easybill_list_customer_groups, easybill_get_customer_group

Article catalogue and stock

easybill_list_positions, easybill_get_position, easybill_create_position, easybill_update_position, easybill_delete_position, easybill_list_stock_entries, easybill_get_stock_entry, easybill_create_stock_entry

Payments

easybill_list_document_payments, easybill_get_document_payment, easybill_create_document_payment, easybill_delete_document_payment

Projects and time tracking

easybill_list_projects, easybill_get_project, easybill_create_project, easybill_update_project, easybill_delete_project, easybill_list_time_trackings, easybill_get_time_tracking, easybill_create_time_tracking, easybill_update_time_tracking, easybill_delete_time_tracking

Attachments and templates

easybill_list_attachments, easybill_get_attachment, easybill_download_attachment, easybill_delete_attachment, easybill_list_text_templates, easybill_get_text_template, easybill_list_pdf_templates

Server

easybill_get_server_info — reports mode, limits and whether the credentials work.

Things worth knowing

The server tells the agent how to sequence work

A plain set of endpoint wrappers leads agents astray. Handed an inbound customer inquiry, Claude's first instinct was to call easybill_list_documents — which cannot answer the actual first question, is this company already a customer?

The server therefore ships MCP server instructions (see src/instructions.ts) with the ordering for common tasks, and easybill_create_document opens with the same sequence:

1. easybill_find_customer     — does the customer exist?
2. easybill_create_customer   — only if not
3. easybill_create_document   — creates a DRAFT
4. review with the user
5. easybill_complete_document — assigns the official number, locks it
6. easybill_send_document     — only when explicitly asked

easybill_list_documents explicitly says it is not the tool for orienting yourself. If you extend this server, keep that pattern: state prerequisites at the top of the description of the tool an agent will reach for first.

All money is in cents

easybill represents every monetary value as an integer in cents, even where the API types it as a float. 1999 means 19.99 EUR. This is stated in every tool description that touches an amount, because getting it wrong produces invoices off by 100×.

Times in time tracking (timer_value) are in minutes.

Drafts vs. completed documents

easybill_create_document produces a draft. It has no official document number and can still be edited. Call easybill_complete_document to finalise it — easybill then assigns the number and locks it.

To void a completed invoice, use easybill_cancel_document (which creates a proper STORNO document), not easybill_delete_document. Completed invoices generally cannot be deleted for legal reasons.

Rate limits are low

easybill allows 10 requests/minute on PLUS and 60 on BUSINESS. The server throttles itself to EASYBILL_RATE_LIMIT_PER_MINUTE and, if a 429 slips through, retries while honouring Retry-After. Set the variable to match your plan — otherwise a broad question that pages through many documents will stall.

Because of this, prefer narrow filters over paging: easybill_list_documents with type='INVOICE' and paid_at='null' costs one request, where scanning everything costs dozens.

Context management

Document has 69 fields and Customer 79. List tools therefore return a compact default field set, and single-record lookups return everything. Both accept fields:

• omit it → compact defaults

• fields: ["number", "amount"] → just those (plus id)

• fields: ["all"] → every field

Responses over EASYBILL_CHARACTER_LIMIT are truncated, halving the item count until they fit, and say so in truncation_message.

No fuzzy customer search

The easybill API has no full-text search. Customer filters match exact values (each accepts several comma-separated). To find a customer by partial name, either use the exact spelling or page through and match locally.

Useful filter recipes

Development

npm run build      # compile to dist/
npm run typecheck  # tsc --noEmit
npm test           # offline suite — 37 tests, no credentials needed
npm run test:live  # read-only tests against a real account (needs .env)
npm run test:all   # both
npm run dev        # watch mode
npm run smoke      # read-only self-test against the live API (needs .env)
npm run inspect    # MCP Inspector against the built server (needs .env)

Tests

npm test runs offline and needs no easybill account — it covers response shaping, the HTTP client against a mock API, the rate-limit throttle, and the MCP surface (schemas, annotations, write-gating, error handling) driven over the real stdio protocol.

test/
├── helpers/mcp-client.mjs  minimal MCP stdio client + mock API server
├── format.test.mjs         field selection, pagination, truncation, markdown
├── client.test.mjs         auth headers, query serialisation, 429 retry, error mapping
├── rate-limit.test.mjs     sliding-window throttle
├── server.test.mjs         tool registration, workflow guidance, validation, errors
└── live.test.mjs           optional: read-only checks against a real account

live.test.mjs skips itself unless EASYBILL_API_KEY is set, so contributors without an account still get a green suite. It only reads — nothing in the test suite writes to easybill.

Project layout:

src/
├── index.ts              entry point, stdio transport, env validation, --selftest
├── instructions.ts       MCP server instructions: workflow ordering for the agent
├── constants.ts          config, summary field sets, enums
├── schemas/common.ts     shared Zod building blocks
├── services/
│   ├── client.ts         HTTP, auth, throttling, retries, error mapping
│   └── format.ts         field selection, pagination, markdown, truncation
└── tools/
    ├── registry.ts       registration + write-gating
    ├── crud.ts           generic CRUD tool factory
    ├── search.ts         fuzzy customer lookup
    ├── documents.ts      documents + lifecycle actions
    ├── customers.ts      customers, contacts, groups
    ├── catalog.ts        positions, stock
    ├── finance.ts        payments
    ├── work.ts           projects, time tracking
    ├── files.ts          attachments, templates
    └── meta.ts           server info

Most resources are generated from a declarative config in crud.ts; only genuinely resource-specific behaviour (document lifecycle, downloads, sending) is hand-written.

Contributing

Issues and pull requests welcome. The tool surface is derived from easybill's official OpenAPI spec (https://api.easybill.de/rest/v1/swagger.json) — when adding a tool, check field names and types against the spec rather than guessing, and mind that monetary fields are cents even where the spec types them as floats.

Disclaimer

This is an unofficial, community-maintained project. It is not affiliated with, endorsed by, or supported by easybill GmbH. "easybill" is a trademark of its respective owner and is used here only to describe what this software talks to.

The software is provided as-is under the MIT license, without warranty. It can create, modify and delete records in your accounting system, and can send invoices to your customers. You are responsible for what you let it do — start read-only, and review what write tools produce before relying on it.

License

MIT © stack74