Lowkey.

Lowkey API

The tax knowledge base of Lowkey,
directly in your own software.

A tax knowledge base that helps you find and map sources fast: legislation, case law, decrees and parliamentary history, with a citation on every answer. This page is the technical integration reference for your developer; for a product overview with pricing, go to the knowledge base page.

Start the trial See the services 14-day free trial. No card required.

§ 01 / Platform

API or MCP: what is the difference?

The API is for software: your portal, filing package or in-house tool calls the knowledge base and gets JSON back. The MCP server is for chat assistants: advisers connect Claude or ChatGPT and ask their questions in plain language. Same knowledge base, same key, same terms.

  API MCP server
Purpose Build the knowledge base into your own software Use the knowledge base from a chat assistant
Who uses it Your developer or software vendor Every adviser at the firm, no developer needed
Connecting HTTPS calls with a Bearer key Server URL plus the same key in Claude or ChatGPT
Cost Included in the monthly subscription Identical: the terms follow the key, not the channel
API · curl
# you receive the base URL with your API key curl "$LOWKEY_API_BASE/v1/search" \ -H "Authorization: Bearer $LOWKEY_API_KEY" \ -G --data-urlencode "q=30% ruling duration"
MCP · remote server config
{ "mcpServers": { "lowkey": { "url": "https://<base-url>/mcp", "headers": { "Authorization": "Bearer <your key>" } } } }

§ 02 / Claude

Works in Claude

The knowledge base connects to Claude as an MCP connector: claude.ai, Claude Desktop and Claude Code. After signing in with a portal account, Claude searches directly across roughly 12,000 tax sources and cites every answer with footnotes back to the source.

Connector URL
https://api.lowkeyautomation.com/mcp
Claude Code · one line
claude mcp add --transport http lowkey-kennisbank \ https://api.lowkeyautomation.com/mcp

Installing requires a portal account. No account yet? Start the trial and you will receive the connector details right after creating your account.

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§ 03 / Services

Services on the platform

01
Live

Tax knowledge base

Validated corpus of Dutch tax sources: legislation, case law, decrees and parliamentary documents. Four endpoints; search and fetching a source are also available as MCP tools.

  • GET /v1/search: search the corpus · included
  • GET /v1/sources/:id: retrieve a source · included
  • GET /v1/status: corpus status · included
  • POST /v1/research: evidence-backed answer with citations · included
02
Early access · on request

30% ruling application

Send employee and employer data (or documents), receive the complete application package for the Dutch tax authority back: the completed form and the accompanying cover letter. The firm keeps its own intake, client relationship and branding.

This endpoint is not yet generally available. Get in touch to discuss early access.

Roadmap: fiscal unity CIT and VAT, the RGS bridging file and more services will follow on the same platform.

§ 04 / Pricing

Pricing

One subscription for the MCP connector and API, from EUR 30 per month excl. VAT for one active user, with tiers for more users. Full pricing and the trial are on the knowledge base page.

Start the trial

§ 05 / Fair use & terms

Fair use and terms

Rate limitsApply at key and firm level. Systematic copying or scraping of the corpus is not permitted.
EU onlyProcessing takes place exclusively on EU-based infrastructure.
No storageNo client data is stored beyond what is needed for the service.

A data processing agreement is available for the 30% ruling application endpoint, since employee and employer data passes through it.

Access

Start the trial

14 days free, no card required. Create a portal account, connect the MCP connector or the API, and pay per month based on active users after the trial.

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