facts

A command-line tool for keeping a project's factual requirements in .facts files and checking them with verification commands.

In plain words
What is it for?
Use it to record facts such as an API returning JSON, a project building, or tests passing, then list, edit, validate, and lint those facts.
Why use it?
It keeps project expectations in one simple format and can show when the actual project no longer matches them.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/av/harbor/facts
Any agent
npx skills add av/harbor --skill facts
Clone the repo
git clone --depth 1 https://github.com/av/harbor

Made for: Claude Code, Codex.

Per session 49 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,274 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 2 findings. Scan, not verified.
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 $0.00049 $0.02274
Opus 5 $0.00024 $0.01137
Sonnet 5 $0.00010 $0.00455
Haiku 4.5 $0.00005 $0.00227

Measured 3d ago against content hash 2e4fcfbe392b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade C, and why

facts scanned grade C with 2 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 3d 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.

Downloads and executes remote codehighSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

curl -fsSL https://raw.githubusercontent.com/av/facts/main/install.sh | sh

Makes network callslowCapability

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

curl -fsSL https://raw.githubusercontent.com/av/facts/main/install.sh | sh
.agents/skills/facts/SKILL.md · 203 lines

How it starts

The opening of the file, as written. The whole thing — 203 lines — stays where its author put it; the contents beside it link to each section on GitHub.

facts

A CLI for fact-driven development. You use it to specify what must be true about a project, then validate that reality matches.

Project: https://github.com/av/facts

Installing

If facts is not installed, install it with one of:

curl -fsSL https://raw.githubusercontent.com/av/facts/main/install.sh | sh
npm install -g @avcodes/facts
pipx install facts-cli

Verify with facts --version. The command is always facts — never npx facts.

Core idea

A .facts file is a flat list of atomic truth statements about a project. Each fact can optionally have a shell command that verifies it. The fact sheet serves as both specification (what should be true) and documentation (what is true) — the difference is just which direction you're working from.

- the API returns JSON
- label: project builds
  command: cargo build
- label: tests pass
  command: cargo test
  tags: [ci, core]

That's the entire format. Plain strings for simple facts, mappings when you need a command, tags, or explicit ID. Allowed mapping keys: id, label, command, tags — nothing else.

Essential commands

Recommended short aliases (all extra arguments are passed through):

  • ll = list --light — the most common "skim" view (markdown headings + dim IDs)
  • ls = list
  • rm = remove
  • at <id> <tag> = edit <id> --add-tag <tag> (supports multiple IDs and --label / --new-id etc. after the tag)
  • rt <id> <tag> = edit <id> --remove-tag <tag>

These are the highest-ROI shortcuts for daily and agent use.

See everything:

facts ll
facts ll --tags "not implemented"
facts ll --has-command
facts list --light                      # or the alias: facts ll

Validate:

facts check
facts check --tags "ci"

check is your primary feedback loop. It lints the files first (aborting on structural errors), then runs every command-fact and reports pass/fail/manual. Run it often. Exit 0 means all command-facts pass; manual facts don't affect the exit code.

Read the full file on GitHub · 203 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. 3d ago First seen · 203 lines · 49 tokens per session scan C 2e4fcfbe392b

Subscribe to this mod's changes

facts is a skill published in the GitHub repository av/harbor (3,202 stars, last pushed 3d ago), licensed Apache-2.0. It adds 49 tokens to every session and 2,274 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it C with 2 findings (downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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