API & MCP

Everything a person can do on Half-Life, Activity & Decay Chain Calculator, a program or AI agent can do with the same inputs and get the identical result.

HTTP API

POST https://prooflinehalflife.usefulweb.app/api/v1/calculate – run Half-Life, Activity & Decay Chain Calculator
GET https://prooflinehalflife.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.

Half-Life, Activity & Decay Chain Calculator

Work out radioactive decay the way textbooks and labs do: how much of a nuclide is left after a time and what its activity is (Bq or Ci, from a percentage, an activity, a mass or a number of atoms), how long it takes to fall to a given level, which half-life fits your measured count rates, and how the members of a decay chain such as Mo-99 → Tc-99m or radon and its progeny grow in and decay (Bateman equations with branching). Nineteen preset nuclides carry evaluated half-lives from ENSDF/NUBASE2020. Part of the Proofline math notebook.

Inputs of Half-Life, Activity & Decay Chain Calculator
Field	Type	Default	Description
`mode`	select (decay, time, fit, chain)	"decay"	Calculation
`nuclide`	select (custom, h3, c14, f18, p32, k40, co60, sr90, mo99, tc99m, i131, cs137, po210, rn222, ra226, th232, u235, u238, pu239, am241)	"custom"	Nuclide
`halfLife`	text	—	Half-life (own nuclide). A number with a time unit: s, min, h, d or y (365.2422 days).
`initial`	text	—	Starting amount. A percentage, an activity (Bq, kBq, MBq, GBq, Ci, mCi, µCi), a mass (g, mg; preset nuclides only) or a number of atoms. Empty: 100 % (chains: 1 MBq).
`elapsed`	text	—	Elapsed time
`target`	text	—	Remaining level (time mode). A percentage, or an activity or mass in the same kind of unit as the start.
`measurements`	textarea	—	Measurements (fit mode). One measurement per line: the time with its unit and the measured count rate or activity.
`chainPreset`	select (custom, mo99-tc99m, sr90-y90, rn222, ra226)	"custom"	Decay chain
`chain`	textarea	—	Chain members (own chain). One member per line: name, half-life (or “stable” for the last) and optionally the share of the previous member’s decays that feeds it.
`duration`	text	—	Follow the chain for. Empty: the preset chain’s own period.

Example request

Iodine-131: 100 MBq after 30 days

curl -X POST https://prooflinehalflife.usefulweb.app/api/v1/calculate -H 'content-type: application/json' -d '{"mode":"decay","nuclide":"i131","initial":"100 MBq","elapsed":"30 d"}'

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://prooflinehalflife.usefulweb.app/mcp – protocol revisions 2026-07-28 (stateless) and 2025-11-25 / 2025-06-18 / 2025-03-26 (initialize handshake).
Tools: proofline_half_life
Local stdio connector: node src/mcp-stdio.ts --tool=proofline-half-life

{
  "mcpServers": {
    "proofline-half-life": { "type": "http", "url": "https://prooflinehalflife.usefulweb.app/mcp" }
  }
}