0s and 1s CIS MCP server
Free calculators for the UK Construction Industry Scheme (CIS), as a remote MCP server and a JSON API. For contractors who pay subcontractors, and the bookkeepers who do it for them.
- MCP server:
https://0sand1s.co.uk/mcp(Streamable HTTP, no sign-in) - REST API:
https://0sand1s.co.uk/api/v1(OpenAPI) - Docs: https://0sand1s.co.uk/developers
No key and no account. Nothing you send is stored. Up to 60 requests a minute from one address, the API and the MCP server together.
Tools
Money goes in as pounds ("1,200.00") and comes back as pence and pounds. Dates are YYYY-MM-DD. Every answer lists the GOV.UK and legislation.gov.uk pages it follows. Answers follow the published rules; they are not tax advice and do not come from HMRC.
Connect
Claude (claude.ai and the desktop app): Customize, Connectors, Add custom connector, then name it 0s and 1s with the URL https://0sand1s.co.uk/mcp.
Claude Code:
claude mcp add --transport http 0sand1s https://0sand1s.co.uk/mcp
Cursor (~/.cursor/mcp.json):
{ "mcpServers": { "0sand1s": { "url": "https://0sand1s.co.uk/mcp" } } }
VS Code (.vscode/mcp.json):
{ "servers": { "0sand1s": { "type": "http", "url": "https://0sand1s.co.uk/mcp" } } }
Try the API
curl "https://0sand1s.co.uk/api/v1/deduction?gross=1200&vat=200&materials=300&rate=20"
About this repository
This repository holds the listing for the official MCP registry (server.json, name uk.co.0sand1s/cis) and this README. The server is hosted by 0s and 1s, CIS filing software for contractors. Questions: [email protected].
