A development workflow for testing claims with outside evidence and small machine-checkable experiments.

Use it to build and assess a graph of claims, research supporting evidence, run deterministic proof-of-concept tests, and audit the results.

It helps separate claims supported by evidence from claims that are disproved or still uncertain, then checks the work independently.

empirica — Skill for Claude Code by obzenner/siffran

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 obzenner/siffran --skill empirica

Clone the repo

git clone --depth 1 https://github.com/obzenner/siffran

Made for: Claude Code.

Or install empirica, the plugin that ships this one along with the rest of its 1 skill, 1 command, 1 agent, 9 hooks, 1 MCP server.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/obzenner/siffran/empirica/github.svg)](https://agentmods.dev/skills/obzenner/siffran/empirica)

Your own site

<a href="https://agentmods.dev/skills/obzenner/siffran/empirica"><img src="https://agentmods.dev/badge/skills/obzenner/siffran/empirica/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/obzenner/siffran/empirica"><img src="https://agentmods.dev/badge/skills/obzenner/siffran/empirica.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 89 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 4,256 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin unknown 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.

Model	Per session	Once invoked
Fable 5.1	$0.00089	$0.04256
Opus 5.5	$0.00036	$0.01702
Sonnet 5.5	$0.00018	$0.00851
Haiku 4.5	$0.00009	$0.00426

Measured 2d ago against content hash d105e6fc4a54, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

empirica scanned grade A with 0 findings 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 2d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/empirica/skills/empirica/SKILL.md · 281 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

Files

What ships with it

8 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

2d ago Changed d105e6fc4a54
9d ago Changed · +43 lines 8dac3e4bd7d3
23d ago Changed · +10 lines 529abef5f7ac
1mo ago Changed · +3 lines cf2d437a3b76
1mo ago Changed · +4 lines 798700c971e1
1mo ago Changed · +11 lines 134a652873e7
1mo ago Changed · +4 lines acb4e68d287d
1mo ago Changed · +2 lines b97b098c2278
1mo ago Changed · -390 lines · -55 tokens per session 90a4e7dd95c7
1mo ago First seen · 594 lines · 144 tokens per session scan A 7190fa6e1a09

Subscribe to this mod's changes

empirica is a skill published in the GitHub repository obzenner/siffran (7 stars, last pushed 3d ago), with no licence file. It adds 89 tokens to every session and 4,256 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Research

empirica next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
empiricaobzenner/siffran	Skill	7	3d ago	none	A	89	Claude Code
imagegenopenai/codex	Skill	134k	today	Apache-2.0	A	113	Codex
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	yesterday	MIT	A	200	Claude Code, Codex
playwright-climicrosoft/playwright	Skill	100k	yesterday	Apache-2.0	A	19	Claude Code
browser-automationopenclaw/openclaw	Skill	394k	today	MIT	A	36	Claude Code
systematic-debuggingobra/superpowers	Skill	314k	4d ago	MIT	A	21	Claude Code
next-cache-components-adoptionvercel/next.js	Skill	143k	today	MIT	A	95	Claude Code