React Native Healthkit

What it does

When your agent uses it

• Code imports either package
• The user asks about HealthKit
• Clinical/FHIR health records
• HealthKit permissions

Example prompts

• “/react-native-healthkit”

Requirements

• Node.js

Workflow steps

12 steps, taken from the first numbered list in SKILL.md.

1. 1iOS only, no Expo Go. Needs a dev client / native build. On Android and web every export is a stub that warns once and returns an…
2. 2Request authorization before any query or subscription for every type you touch. Querying a type you never requested can crash the app. A…
3. 3Read permission is invisible. HealthKit never tells you whether reading was denied: you just get no samples. authorizationStatusFor() only…
4. 4Identifiers are string literals, e.g. 'HKQuantityTypeIdentifierStepCount', not enums. Type names drop the HK prefix…
5. 5limit is required on sample queries. limit: 0 (or negative) means "all". Results are newest first unless ascending: true.
6. 6Units are HKUnit strings ('count', 'count/min', 'kg', 'kcal', 'mg/dL', '%', 'ms') and are typed per identifier. Omit unit to get the…
7. 7Dates are JS Date objects both in and out.
8. 8Prefer statistics queries over raw samples for totals and averages (steps per day, average heart rate). queryStatisticsForQuantity /…
9. 9Workouts and sources are native proxies. Call toJSON() before putting them in state or storage, and dispose() them when iterating large…
10. 10Metadata keys use the serialized name, not the Swift constant name: HKExternalUUID, not HKMetadataKeyExternalUUID.
11. 11Newer identifiers need newer iOS. The types include identifiers up to the latest SDK. On older iOS, requestAuthorization silently drops…
12. 12Anchors are opaque base64 strings. Persist newAnchor after each successful sync. An invalid anchor throws; omit anchor to start over.

What it can do on your machine

Read from SKILL.md and the folder at commit 9854ae3. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • npx

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md. Its commands use npx, which can reach the network depending on how they are called.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

React Native Healthkit loads about 1.6k tokens when it runs, and up to ~13k if it reads all its reference files. Until then it costs about 118 tokens; SKILL.md has 567 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~118

When it runs · the whole SKILL.md, loaded when a task matches

~1.6k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~13k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from kingstinct/react-native-healthkit at commit 9854ae3, republished under its MIT licence (© kingstinct). 567 words, ~1,590 tokens.

name

react-native-healthkit

description

How to use @kingstinct/react-native-healthkit (and its sibling @react-native-healthkit/health-records) to read, write and subscribe to Apple HealthKit data from React Native / Expo apps. Use whenever code imports either package, when the user asks about HealthKit, Apple Health, steps, heart rate, sleep, workouts, clinical/FHIR health records, HealthKit permissions, background delivery or the healthkit Expo config plugin in a React Native project.

npx expo install @kingstinct/react-native-healthkit react-native-nitro-modules

{ "expo": { "plugins": [["@kingstinct/react-native-healthkit", {
  "NSHealthShareUsageDescription": "We read your steps to show daily progress",
  "NSHealthUpdateUsageDescription": "We save your workouts to Apple Health",
  "background": true
}]] } }

import {
  isHealthDataAvailable,
  requestAuthorization,
  queryStatisticsForQuantity,
} from '@kingstinct/react-native-healthkit'

if (isHealthDataAvailable()) {
  await requestAuthorization({
    toRead: ['HKQuantityTypeIdentifierStepCount'],
    toShare: ['HKQuantityTypeIdentifierBodyMass'],
  })

  const startOfDay = new Date()
  startOfDay.setHours(0, 0, 0, 0)

  const { sumQuantity } = await queryStatisticsForQuantity(
    'HKQuantityTypeIdentifierStepCount',
    ['cumulativeSum'],
    { filter: { date: { startDate: startOfDay } } },
  )
  console.log(sumQuantity?.quantity, sumQuantity?.unit) // 4231 'count'
}

© kingstinct, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 8 other files (references) in skills/react-native-healthkit of kingstinct/react-native-healthkit.

• SKILL.md
• references/apple-docs.md
• references/authorization.md
• references/health-records.md
• references/querying.md
• references/setup.md
• references/subscriptions-and-background.md
• references/workouts-and-other-types.md
• references/writing.md

Open the folder on GitHubat commit 9854ae3