API & MCP

Everything a person can do on Wheel Spinner with Weights, a program or AI agent can do with the same inputs and get the identical result.

HTTP API

POST https://fielddaywheelspinner.usefulweb.app/api/v1/calculate – run Wheel Spinner with Weights
GET https://fielddaywheelspinner.usefulweb.app/api/v1/tool – inputs, output schema, examples
OpenAPI 3.1: /openapi.json · /openapi.yaml
Errors: application/problem+json; 422 includes per-field errors.

Wheel Spinner with Weights

Spin a decision wheel where each segment can have its own weight (3 × pizza, 1 × sushi). The odds are exactly weight ÷ total, the organiser can publish a SHA-256 fingerprint before the spin, and the result replays identically here.

Inputs of Wheel Spinner with Weights
Field	Type	Default	Description
`segments` (required)	table	—	Segments
`spins`	integer	1	Spins
`removeWinners`	boolean	true	Remove each winner before the next spin
`secret`	text	—	Secret (revealed after the draw). The organiser’s random secret. Its fingerprint is shown before the draw; empty = derived from the entries (predictable, only for demos).
`audienceWord`	text	—	Audience word (optional). A word someone calls out after the fingerprint is shown. It changes the draw, so the organiser cannot steer it.

Example request

Dinner wheel: pizza three times as likely as sushi

curl -X POST https://fielddaywheelspinner.usefulweb.app/api/v1/calculate -H 'content-type: application/json' -d '{"segments":[{"label":"Pizza","weight":3},{"label":"Sushi","weight":1},{"label":"Tacos","weight":2},{"label":"Curry","weight":2}],"spins":1,"secret":"c41d0e9b7a2f","audienceWord":"hungry"}'

Every result contains

inputs (normalised, defaults applied), summary, result (validated against the published schema), units, assumptions, sources, warnings, computedAt and links.

MCP (Model Context Protocol)

Streamable HTTP endpoint: https://fielddaywheelspinner.usefulweb.app/mcp – protocol revisions 2026-07-28 (stateless) and 2025-11-25 / 2025-06-18 / 2025-03-26 (initialize handshake).
Tools: fieldday_wheel_spinner
Local stdio connector: node src/mcp-stdio.ts --tool=fieldday-wheel-spinner

{
  "mcpServers": {
    "fieldday-wheel-spinner": { "type": "http", "url": "https://fielddaywheelspinner.usefulweb.app/mcp" }
  }
}