rb209-mcp

MCP server exposing the AHDB RB209 (Nutrient Management Guide) Web API v2 — 94 tools — plus a nutrient-planning skill.

The three Users auth endpoints (Login / Logout / Refresh_Token) are deliberately not exposed: the server manages that token lifecycle itself, so a tool call to Logout could only ever invalidate its own session.

The extension ships its own usage guidance, so installing the .mcpb in Claude Desktop is enough — you don't need to load the skill separately. The server exposes an MCP instructions brief on connect, and the highest-risk tools (notably the recommendation endpoint) carry the must-know rules in their tool descriptions. skill/rb209-nutrient-planning/SKILL.md remains the fuller guide (for Claude Code / claude.ai and as a versioned release asset); the embedded guidance is a condensed subset kept in sync with it by hand.

Tools are a faithful passthrough to the API with one deliberate exception: the recommendation endpoint has a footgun where a missing field.grass (which the API's validation does not report) makes the call fail with the misleading 422 "…calculating the crop order". For that endpoint only, the server fills the incidental required-empty sections (grass, grassland, organicMaterials, mannerOutputs) when they are absent — never overwriting supplied data, and with no effect on the result. See src/recommendationGuardrail.ts.

Requirements

You need your own AHDB RB209 Web API licence (register at https://rb209.ahdb.org.uk/Home/RequestAccess). Each user supplies their own credentials; they never leave your machine.

Install (non-technical — Claude Desktop)

1. Download rb209-mcp.mcpb from the latest Release.

2. Double-click it; Claude Desktop opens the installer.

3. Enter your RB209 email and password in the settings form.

4. Done — the RB209 tools appear in your chat tool.

Install (developers)

npm install && npm run build
RB209_EMAIL=you@example.com RB209_PASSWORD=secret node dist/index.js

Add to an MCP client config with command: node, args: [".../dist/index.js"], and env: { RB209_EMAIL, RB209_PASSWORD }.

Configuration

Development

npm test          # unit tests (msw-mocked)
npm run test:watch
RB209_EMAIL=... RB209_PASSWORD=... npm test   # also runs the live integration test

This server is released under the MIT Licence. The RB209 data it returns is licensed API content © AHDB under the Open Government Licence v3.0.