API & MCP

Everything a person can do on Plinko Name Picker, a program or AI agent can do with the same inputs and get the identical result.

HTTP API

POST https://fielddayplinkopicker.usefulweb.app/api/v1/calculate – run Plinko Name Picker
GET https://fielddayplinkopicker.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.

Plinko Name Picker

Pick one or more names with a physics plinko board. The organiser publishes a SHA-256 fingerprint of a secret before the drop, the audience adds a word, and afterwards anyone can replay the exact drop here and check that every name had the same chance.

Inputs of Plinko Name Picker
Field	Type	Default	Description
`names` (required)	list	—	Names (one per line)
`picks`	integer	1	How many to pick (one ball each, winners leave the board)
`rows`	integer	12	Peg rows
`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.
`checkDrops`	integer	0	Fairness check: extra test drops (0 = off). Counts where test balls land and which names they pick, to show the board’s bias and that names are still equally likely.

Example request

Who picks the film tonight? (secret + audience word)

curl -X POST https://fielddayplinkopicker.usefulweb.app/api/v1/calculate -H 'content-type: application/json' -d '{"names":["Ana","Ben","Cleo","Dev","Eli","Fay"],"picks":1,"rows":12,"secret":"7f3a9c2e51d84b06","audienceWord":"pineapple"}'

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://fielddayplinkopicker.usefulweb.app/mcp – protocol revisions 2026-07-28 (stateless) and 2025-11-25 / 2025-06-18 / 2025-03-26 (initialize handshake).
Tools: fieldday_plinko_picker
Local stdio connector: node src/mcp-stdio.ts --tool=fieldday-plinko-picker

{
  "mcpServers": {
    "fieldday-plinko-picker": { "type": "http", "url": "https://fielddayplinkopicker.usefulweb.app/mcp" }
  }
}