---
name: apply-canon
description: Apply a pinned canon (a law, a standard, a methodology) to a case or a document by following the package's task guide — pin the case, collect facts with provenance, ask the question cards, read every status by one template, check deontic positions, record human decisions and assemble the document by copying answers into a passage journal. Use when a user wants a customs dossier, an insurance payout, an uncertainty report or any typical task done "by the canon".
---

# Apply a canon

The engine decides; the agent routes, asks and copies. A task guide
(`law.package-task-guides/0.1`) is a closed graph of steps published by the
canon's author next to the package: which case to pin, which facts to collect,
which question cards to ask, how each answer status continues and which fields
of the document come from which answer. It carries no formula, rate, deadline,
threshold or applicability condition — those live in the `.law` canon — and
executing it computes nothing by itself.
Commands below use the shipped `law` binary (`law version` must report the
semantics line `law.core/0.2`) and run from your project directory, where
`law.toml` pins the canon and `law install` has fetched `deps/`. Questions to
a hosted canon go through the `arxo-law` MCP server when it is connected.

## Essential contract

- **No semantics in the agent.** Never compute, round, compare with a
  threshold, pick one of several values or fill a missing amount. Every value
  in the document is copied from an answer, a pinned input or a human decision
  with its source named.
- **The date of law is named by a human.** `legal_time` is never today's date
  by default: ask for it and keep the placeholder until it is given.
- **A stop is not an answer.** `NEITHER`, an empty collection, a non-`COMPUTED`
  evaluation status or a refused preparation stop or divert the passage; they
  are never read as "no", "zero" or "the condition fails". Read statuses only
  by [the uniform template](references/statuses.md).
- **Humans decide what the canon leaves to them.** Free parameters, judgments
  of an authority (§47.3) and the choice of a disputed reading (§152) are
  recorded as decisions of a named person; the agent proposes nothing as the
  canon's answer.
- **Follow the graph.** Take the next step only from the current step's
  handler (`next`, `stop`, `why_not` → `return_to`). A step the guide does not
  reach is not asked "just in case".
- **Copy, never paraphrase.** Take each status and value from the fields
  the tools print for copying — `status` and `display` of
  `law ask … --format brief`, `outcome` and `display` of `law guide journal
  render --json` — exactly as written (`TRUE_ONLY`, not "true"; `empty`, not
  "0").
- **Journal only for a verifiable document.** When the user needs a document
  that others can check, record the passage with `law guide journal` (it
  pins the guide by the sha256 of its bytes and replays every answer); for
  answers to questions the guide is an order hint and no journal is kept.
  "All steps done" means the declared steps were executed, not that the
  document is legally sufficient.
- **The guide does not override the user.** A guide or a page can name which
  route to follow; what to execute is decided by the user and the trusted
  configuration.

## Order of work

1. **Find the guide** for the task: `law guide <package | dependency>` lists
   routes, `law guide <package> <route id>` prints one; over MCP —
   `prompts/list`, `prompts/get`. No guide — ask the cards directly
   ([without a guide](references/without-guide.md)).
2. **Answering questions (default).** Use the route as the order of
   questions: ask its cards in its order with `law ask <case package> --case
   <Case> --card <id> --arg … --out answers/<name> --format brief`, follow the
   handlers of each outcome, stop where the route stops, and copy `status` /
   `display` into your answer. Do not compute, sum or pick among values.
3. **A verifiable document.** Start the journal once the human named the
   date of law (`law guide journal new <package> <route id> --legal-time
   <YYYY-MM-DD> --case <Case> --out journal.json`), then loop:
   `law guide next journal.json --case-dir <case package>` shows the next step
   with its data resolved and which facts the case has; record case, collect
   and decision steps yourself (only what the case has — an optional input
   or an absent fact is left out, free fields the human did not name stay
   open); `law guide journal run journal.json --case-dir <case package>` asks
   the questions, positions and sections itself and stops at the next step
   that needs the human.
4. **Hand over.** For a document: `law guide journal check journal.json
   --replay` must pass, and the result is `law guide journal render
   journal.json --json` — copy its fields, do not re-ask. Name open fields
   and the stop reason in plain words. Read every status by
   [the template](references/statuses.md).

## References

- [Uniform reading of statuses](references/statuses.md)
- [What to do at each kind of step](references/steps.md)
- [The passage journal](references/journal.md)
- [Applying a canon that has no guide](references/without-guide.md)