fitness-correlations

fitness-correlations is a skill for Claude Code from philipyaz/cos. It costs 209 tokens per session (2,104 once invoked), scanned A, original, MIT.

A fitness interpretation skill for sleep and workout data recorded from Apple Watch and training sessions. The system calculates Pearson correlation and linear regression, while the skill explains what those statistics may mean.

In plain words
What is it for?
Use it to explore whether sleep duration or deep sleep is associated with performance, and to discuss the results with appropriate health-data caution.
Why use it?
It turns statistical results into plain-language observations and practical guidance. It also makes clear that a correlation is an association in the logged data, not proof that one factor causes the other.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Good fit Use it to explore whether sleep duration or deep sleep is associated with performance, and to discuss the results with appropriate health-data caution.

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Install with agentmods
npx agentmods add skills/philipyaz/cos/fitness-correlations
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add philipyaz/cos --skill fitness-correlations
Clone the repo
git clone --depth 1 https://github.com/philipyaz/cos

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for fitness-correlations

README.md
[![agentmods](https://agentmods.dev/badge/skills/philipyaz/cos/fitness-correlations/github.svg)](https://agentmods.dev/skills/philipyaz/cos/fitness-correlations)
Your own site
<a href="https://agentmods.dev/skills/philipyaz/cos/fitness-correlations"><img src="https://agentmods.dev/badge/skills/philipyaz/cos/fitness-correlations/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for fitness-correlations

Your own site · 80×15
<a href="https://agentmods.dev/skills/philipyaz/cos/fitness-correlations"><img src="https://agentmods.dev/badge/skills/philipyaz/cos/fitness-correlations.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 209 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,104 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00209 $0.02104
Opus 5 $0.00105 $0.01052
Sonnet 5 $0.00042 $0.00421
Haiku 4.5 $0.00021 $0.00210

Measured 10d ago against content hash 6d034886fb69, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

fitness-correlations scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

health-data plumbing runs **only** through the **`fitness`** MCP — never `bash`/`curl`.
board/.claude/skills/fitness-correlations/SKILL.md · 141 lines

How it starts

The opening of the file, as written. The whole thing — 141 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fitness correlations (the sleep ↔ performance interpreter)

This skill answers "how does my sleep affect my performance?" It is the interpret half of a deterministic compute: the board computes the statistics (Pearson r for sleep-vs-performance and deep-sleep-vs-performance, plus a linear regression) — you do not. The board is a state machine; the math is the board's, the meaning is yours. There is no board-side LLM here either — get_correlations runs pure, repeatable stats and persists the snapshot; your job is to trigger that compute via the fitness MCP, then read the numbers back to the user in plain language with actionable guidance. The health-data plumbing runs only through the fitness MCP — never bash/curl.

This skill mostly READS + interprets. It does not usually write — get_correlations already computes and persists the snapshot, so you almost never call save_correlation_report (that writer is for an externally-computed dataset the user supplies — see the guardrail).

NOT MEDICAL ADVICE — and NOT causation. A correlation between sleep and performance is an observational association across your logged data, not proof that sleep causes the performance change — say so, in your own words. And it is informational, not medical advice: defer any injury, illness, abnormal symptom, pregnancy, or an under-18 user to a physician / physiotherapist / qualified coach; don't push hard training off a number.

Gate. get_correlations is a read/compute — it works whether or not the Fitness add-on is enabled (reads are always open). The persist it does is add-on-gated: it lands when the add-on is enabled and is skipped (404) when it's off — tell the user to enable it at /addons if you need the snapshot to stick.


PROCEDURE — compute (board), then interpret (you)

1. COMPUTE — get_correlations({ days }) (the board's deterministic stats)

Call get_correlations with the window the user asked for:

Read the full file on GitHub · 141 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 10d ago First seen · 141 lines · 209 tokens per session scan A 6d034886fb69

Subscribe to this mod's changes

fitness-correlations is a skill published in the GitHub repository philipyaz/cos (4 stars, last pushed today), licensed MIT. It adds 209 tokens to every session and 2,104 once invoked, about $0.0010 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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