yuki-mcp

A Model Context Protocol (MCP) server that connects AI agents to Yuki accounting via Yuki's SOAP API.

Built with Node.js, TypeScript, and @modelcontextprotocol/sdk.

Installation

npm install @codemill-solutions/yuki-mcp

Then add it to your MCP host configuration (e.g. claude_desktop_config.json):

{
  "mcpServers": {
    "yuki": {
      "command": "node",
      "args": ["node_modules/@codemill-solutions/yuki-mcp/dist/index.js"],
      "env": {
        "YUKI_API_KEY": "your-api-key-here",
        "YUKI_DOMAIN_ID": "your-administration-guid-here"
      }
    }
  }
}

Prerequisites

• Node.js 20+
• A Yuki account with API access enabled
• Your Yuki API key (Yuki → Settings → API)

Setup

1. Install dependencies

npm install

2. Configure environment variables

cp .env.example .env

Edit .env:

YUKI_API_KEY=your-api-key-here
YUKI_DOMAIN_ID=your-administration-guid-here  # optional at startup

YUKI_DOMAIN_ID can be left empty — the server starts without it. Call get_administrations to discover the correct GUID, then pass it via the administrationId parameter on individual tools.

3. Build

npm run build

4. Connect to an MCP host

Add to your MCP host configuration (e.g. claude_desktop_config.json):

{
  "mcpServers": {
    "yuki": {
      "command": "node",
      "args": ["/absolute/path/to/yuki-mcp/dist/index.js"],
      "env": {
        "YUKI_API_KEY": "your-api-key-here",
        "YUKI_DOMAIN_ID": "your-administration-guid-here"
      }
    }
  }
}

Multi-administration support

If you manage multiple Yuki administrations (each with its own API key), you can supply a JSON file that maps every administrationId to its corresponding API key. The server then authenticates per administration automatically — no single shared key required.

Keys file format

{
  "a1b2c3d4-0000-0000-0000-000000000001": "api-key-for-admin-1",
  "a1b2c3d4-0000-0000-0000-000000000002": "api-key-for-admin-2"
}

Path resolution (first match wins)

Environment variable

YUKI_API_KEYS_FILE=/path/to/your/api-keys.json

When a keys file is present, YUKI_API_KEY becomes optional — the file keys are used for all administration-specific tool calls, and YUKI_API_KEY (if set) serves as the fallback for tools that don't target a specific administration (e.g. get_administrations).

If neither YUKI_API_KEY nor a keys file is found at startup, the server logs a warning but continues running — tools will return an error when called.

Available tools (29)

Administrations

Relations

Sales invoices

Purchase invoices

Transactions & bank

Accounting

Accounting info

Richer read-only views from the AccountingInfo.asmx service — not available through the standard Accounting.asmx.

Documents

Backoffice

Testing

Option 1 — MCP Inspector (tool-level, no LLM)

npm run inspect

Opens a browser UI at http://localhost:5173 where you can call individual tools and inspect raw responses.

Option 2 — Agent test harness (with Claude)

Runs a full agentic loop: Claude reasons about the task, calls tools, and returns a final answer — exactly as an AI agent would use this MCP.

Add your Anthropic API key to .env:

ANTHROPIC_API_KEY=sk-ant-...

Then run a scenario:

npm run agent                                              # default: get_administrations
npm run agent -- --scenario outstanding-invoices
npm run agent -- --scenario search-relations --arg "Bedrijf BV"
npm run agent -- --scenario gl-accounts
npm run agent -- --scenario bank-transactions --arg "1200"
npm run agent -- --scenario full-workflow

Available scenarios: get-administrations, search-relations, outstanding-invoices, outstanding-payables, gl-accounts, bank-transactions, full-workflow.

Architecture

src/
├── index.ts                  # Entry point — loads env + keys file, registers tools, starts stdio transport
├── yuki-client.ts            # SOAP client: per-key session cache, envelope builder, axios HTTP, fast-xml-parser
└── tools/
    ├── administrations.ts    # get_administrations, get_administration_id
    ├── relations.ts          # search_relations, upsert_contact
    ├── invoices.ts           # get_sales_invoices, get_purchase_invoices,
    │                         # process_sales_invoice, process_purchase_invoice
    ├── transactions.ts       # get_transactions, get_transaction_details, process_journal
    ├── accounting.ts         # get_gl_accounts, get_gl_accounts_fiscal, get_net_revenue
    ├── accounting-info.ts    # get_gl_account_scheme, get_period_table,
    │                         # get_gl_transactions_detailed, get_transaction_document,
    │                         # get_start_balances
    ├── documents.ts          # upload_document, upload_document_from_path,
    │                         # get_document_folders, list_documents, search_documents,
    │                         # get_document, download_document, get_cost_categories
    └── backoffice.ts         # get_workflow, get_outstanding_questions

scripts/
└── test-agent.ts             # Agent test harness (Claude + MCP client loop)

Auth flow

Yuki uses a two-step authentication pattern:

1. Authenticate(accessKey) → returns a temporary sessionID
2. All subsequent calls include that sessionID

YukiClient.getSessionID(adminId?) handles this transparently. When called with an administrationId, it resolves the matching API key from the loaded keys map. Session IDs are cached per API key for the lifetime of the process — Authenticate is only called once per key, not once per tool call.

Note: Parameter casing differs across Yuki's services — sessionId (lowercase d) on Sales.asmx and Purchase.asmx; sessionID (uppercase D) on Accounting.asmx, AccountingInfo.asmx, Contact.asmx, and Archive.asmx. This is handled per-tool.

XML documents

Write tools (process_sales_invoice, process_purchase_invoice, process_journal, upsert_contact) pass structured data to Yuki as an XML string inside the xmlDoc SOAP parameter. The XmlValue wrapper ensures this XML is embedded raw (not entity-encoded) in the SOAP envelope. All user-supplied values are XML-escaped via escapeXml().

Rate limits

Yuki enforces 1,000 API requests per day (upgradeable to 5,000–10,000). Each tool call is 1 request. Session IDs are cached so Authenticate is only called once per API key per server process, not once per tool call.

Design agent workflows to fetch broad lists once and reference them from the agent's context window rather than re-fetching on every step.

Troubleshooting

About CodeMill Solutions

CodeMill Solutions is a Dutch software company based in the Netherlands. We build smart, scalable, and customized solutions that help organizations grow, optimize processes, and realize their digital ambitions.

Our services include:

• Custom applications — portals, dashboards, business software, and fully tailored platforms that truly add value.
• API integrations — connecting your application with other systems and external platforms via smart API connections.
• Mobile apps — iOS and Android apps as a logical extension of your web application(s).

yuki-mcp is one of our open-source integrations, making Yuki's accounting platform accessible to AI agents through the Model Context Protocol.

📧 info@codemill.dev 🌐 codemill.dev 💼 LinkedIn 🐙 GitHub

License

MIT — see LICENSE.