Facts Discover

facts-discover

You are a fact sheet maintainer. Your job is to scan the codebase, classify every fact by lifecycle stage, and add missing truths — in a single session.

When to use this skill

This skill classifies facts and syncs the fact sheet with reality. Only use when the user explicitly asks to discover, audit, or sync facts. If the user says "work on facts" or "add facts", they want to define spec — use the facts skill instead, not this one.

Goal

After running this skill, every fact should have the correct lifecycle tag:

• @draft — the fact is vague or high-level; needs refinement before it can be implemented (e.g. "this project supports stripe payments")
• @spec — the fact is precise and actionable, but the code doesn't back it up yet (e.g. "POST /payments creates a Stripe PaymentIntent and returns the client secret")
• @implemented — the fact is true and the codebase proves it
• Untagged — ground truth discovered from the codebase; already verified by observation

Additionally, add facts about important truths not yet in the fact sheet (these go in untagged, since they're already true), fix inaccurate facts, and remove obsolete ones.

Facts with good validation commands are self-enforcing — they catch regressions automatically. But a manual fact is better than a fact with a useless command. A command that always passes regardless of whether the fact is true gives false confidence and is worse than no command at all. Only add a command when it genuinely tests the claim.

Process

1. Load the current fact sheet

Run facts list to see all current facts. Note which sections exist and what they cover.

Run facts check to see which command-facts pass and which fail. Failing facts are candidates for removal or correction.

2. Scan the codebase

Build a comprehensive mental model of the project. Use subagents to scan different areas in parallel for large codebases:

• Project structure, languages, frameworks, build system
• Main components, modules, and their relationships
• Public APIs, interfaces, and contracts
• Testing, CI, and deploy tooling
• Dependencies and their roles
• Conventions and patterns

Each subagent should report back a list of factual observations about its area — not opinions, not aspirations, just what is true now.

3. Classify facts by lifecycle stage

For each existing fact, check it against the codebase and assign the correct lifecycle tag:

• True and code-backed → tag @implemented: facts edit <id> --add-tag "implemented"
• Precise and actionable, but code doesn't exist yet → tag @spec: facts edit <id> --add-tag "spec"
• Vague or high-level, not yet actionable → tag @draft: facts edit <id> --add-tag "draft"
• Partially true — edit the label first, then classify: facts edit <id> --label "corrected statement"
• False or obsolete — remove: facts remove <id>
• Missing validation — the fact could be verified by a command but lacks one: facts edit <id> --command "check command"

When a fact already has a lifecycle tag, verify it's still correct. An @implemented fact whose code was removed should be reclassified to @spec. A @draft fact that was refined elsewhere should be updated.

When removing facts, check if the concept has evolved rather than disappeared — edit instead of remove+add when the same idea persists in a new form.

3b. Add commands to manual facts

Go through manual facts and ask: can this be checked with a short shell command that would actually fail if the fact became false?

That second part is the hard filter. Before adding a command, apply this test:

If someone changed the codebase so this fact was no longer true, would the command fail?

If the answer is no — or only maybe — leave the fact manual.

What makes a command meaningful

A command validates a fact when it checks the claim itself, not just the existence of related code. The command should be:

• Falsifiable — would actually break if the fact became untrue
• Fast — runs in under a second (grep, test, jq, wc, head)
• Idempotent — read-only, no side effects
• Stable — does not break on unrelated changes (avoid line-count checks, match patterns not positions)
• Silent on success — exit 0 means the fact holds, non-zero means it doesn't

Good commands check concrete, specific things:

# Dependency exists in manifest
grep -q '^clap' Cargo.toml
grep -q '"express"' package.json

# File or directory exists
test -f tests/cli.rs
test -d src/components

# A specific value or setting in config
jq -e '.scripts.test' package.json >/dev/null
grep -q 'edition = "2024"' Cargo.toml

# Build or test suite passes
cargo build --quiet 2>/dev/null
npm test --silent

# A property holds (or does not hold) across the codebase
! grep -rq 'unsafe' src/
! grep -rq 'unwrap()' src/handlers/

# Count-based invariants (use ranges, not exact numbers)
test $(find src -name '*.rs' | wc -l) -ge 10

# Behavioral test — actually exercise the tool
facts list --help 2>&1 | grep -q '\-\-section'
echo '- test fact' | facts lint /dev/stdin 2>/dev/null

What makes a command useless

The most common failure mode is keyword grepping: picking a word from the fact label and checking that it appears somewhere in a source file. This doesn't validate the fact — it validates that the codebase uses similar vocabulary.

# BAD: "heading depth maps to hierarchy"
grep -q "depth" src/parser.rs
# This checks that the word "depth" appears in the file. It would pass
# even if depth handling was completely broken. It would fail if someone
# renamed the variable to "level" even though the behavior is unchanged.

# BAD: "tags are freeform tokens for filtering and categorisation"
grep -q "tags" src/model.rs
# The word "tags" will always be in a file that deals with tags.
# This tells you nothing about whether they're freeform or used for filtering.

# BAD: "commands run sequentially"
! grep -q "async\|tokio" src/check.rs
# Absence of async doesn't prove sequential execution — there are other
# ways to run things concurrently. And this would still pass if someone
# added parallelism via std::thread.

# BAD: "the CLI treats sections as first-class citizens"
grep -q "section" src/list.rs
# What does this even check? That the word "section" appears? Of course it does.

The pattern to watch for: if your command is grep -q "<keyword from the fact>" <file that obviously contains that keyword>, it's not a real check. Stop and either find a meaningful command or leave the fact manual.

When to leave facts manual

Not every fact can or should have a command. Leave facts manual when they are:

• Subjective or qualitative — "extreme simplicity", "codebase is DRY", "polished UX"
• About human processes — "bump version, commit, push"
• About external systems you can't query locally
• About behavior that would require a complex integration test to verify and is already covered by the project's test suite
• About design intent — "each fact is atomic and independent", "file order is canonical"
• Only checkable via keyword grep — if the only command you can write checks for a keyword rather than the actual claim, leave it manual

A fact sheet with 30 genuinely validated facts and 20 honest manual facts is far more useful than one with 50 commands that are all grep -q "<word>" <file>.

4. Add missing facts

Identify important truths not yet in the fact sheet. Add them with facts add:

facts add "the project uses PostgreSQL for persistence" --section architecture \
  --command "grep -q 'postgres' docker-compose.yml"
facts add "project builds successfully" --command "cargo build --quiet" --section ci

Prefer facts that are:

• Atomic — one truth per fact
• Verifiable — include a check command when one can meaningfully validate the claim
• Stable — unlikely to change with every commit
• Useful — helps an agent understand or validate the project

Do not add trivially obvious facts ("the project has files") or volatile ones ("there are 47 tests").

5. Organize

Group related facts into sections using --section. Section paths support nesting (e.g. api/auth, cli/subcommands). Keep sections focused — split broad ones.

6. Validate and report

Run facts check to confirm all command-facts pass (this also lints the files).

Report what changed: facts added, edited, removed, commands added. If any areas of the codebase were ambiguous or couldn't be fully captured, say so.

Guidelines

• Keep fact labels concise and declarative.
• Command quality matters more than command count. A command that doesn't actually test the fact is worse than no command — it creates false confidence. Only add commands that would break if the fact became false.
• When writing check commands, prefer grep -q, test -f, test -d, jq -e, and similar fast read-only checks. Avoid commands that build, install, or modify anything unless that is the point of the fact (e.g. "project builds successfully").
• Use tags to categorize when useful (e.g. @ci, @api, @core). Use --add-tag and --remove-tag for incremental tag changes.
• Sections with no remaining facts are cleaned up automatically by the CLI.
• Lifecycle classification is the primary job. Every fact should end up with the right lifecycle tag (@draft, @spec, @implemented) or no tag (ground truth). Do not remove @draft or @spec facts — classify them, don't delete aspirational work.
• When adding new facts you discovered from the codebase, leave them untagged — they are already true by observation.

Example session

# Load current state
facts list
facts check

# Spawn subagents to scan the codebase:
# Subagent 1: project structure, build system, dependencies
# Subagent 2: API surface, routes, contracts
# Subagent 3: testing, CI, deploy

# Classify existing facts by lifecycle stage:

# This fact is true — code proves it
facts edit x1z --add-tag "implemented"

# This fact is precise but the code doesn't exist yet
facts edit a2b --add-tag "spec"

# This fact is vague ("supports payments") — needs refinement
facts edit c3d --add-tag "draft"

# An old fact about Python is no longer true — project migrated to Rust
facts remove p2q

# Found a new truth while reading code — add untagged (ground truth)
facts add "API rate limits to 100 req/min per key" --section api/limits \
  --command "grep -q 'rate_limit.*100' src/middleware.rs"

# Verify everything
facts check

# Report: 5 classified (@implemented: 3, @spec: 1, @draft: 1), 1 added, 1 removed