From your first SIGN file to an agent that uses it.

Clone the specification and validate the examples.

The sign-lang repository holds the specification, six worked examples and the validator. The validator has no dependencies, so there is nothing to install.

git clone https://github.com/sign-protocol/sign-lang.git
cd sign-lang
node validator/bin/sign.js validate --source examples

The last line of the output should read:

pass — 11 documents across 6 file(s)

To type sign instead of node validator/bin/sign.js, run npm link inside the validator folder. The rest of this guide uses the full path so it works either way.

Read one document before you write one.

Open examples/02-full-document.sign. Each block starts with a sigil: a symbol that tells the agent what kind of content follows. These are the first lines:

@doc WFI-008 [std, active, agents+employees] v2 sha:7d4a1f
@links WFI-001,WFI-002,WFI-003,WFI-009
@cycle 90d
@reviewed 2026-04-14

@vocab
  depends_on    | skill cannot be effectively applied without target present
  adjacent_to   | skills frequently co-occur and complement; symmetric

@def skill
  Atomic, distinct, demonstrable capability enabling effective task performance.

• @doc gives the ID, the document type, the status, who it is for, and the version.
• @links names related documents. The validator checks that each one exists.
• @cycle and @reviewed say how often the document is reviewed and when it last was.
• @vocab defines every relationship word the document uses.
• @def holds a definition.

Keep the sigil quick reference open while you write. Block order matters: the validator fails a document whose blocks are out of order.

Write two documents that link to each other.

Make a folder called knowledge next to sign-lang and add these two files. They describe a refund rule and the role it depends on. The ## line is the one-sentence summary that goes into the index.

@doc REFUND-001 [std, active, agents+employees] v1
@links REFUND-002
@cycle 90d
@reviewed 2026-11-09
## Refunds over 500 dollars need a manager's approval before an agent issues them.

@vocab
  approved_by | the refund is approved by the named role before it is issued

@def refund
  Money returned to a customer against a paid invoice.

@rules
  1. An agent may issue a refund of 500 dollars or less without approval.
  2. A refund over 500 dollars needs approval from a support manager first.

@constraints
  manager-approval
    requires: support-manager approval on any refund over 500 dollars
    forbids: an agent issuing a refund over 500 dollars without that approval

@doc REFUND-002 [ref, active, agents] v1
@links REFUND-001
@cycle 180d
@reviewed 2026-11-09
## Who counts as a support manager for refund approvals.

@def support-manager
  A person in the Support Managers group in the HR system.

node sign-lang/validator/bin/sign.js validate --source knowledge

You should see pass — 2 documents across 2 file(s). Now change @links REFUND-002 to REFUND-003 and validate again: the validator reports that no document with that ID exists. Change it back before you continue.

Compile the canon into an index and a bundle.

Compiling validates first, then writes the two layers an agent consumes.

node sign-lang/validator/bin/sign.js compile --source knowledge --output dist

• dist/canon-index.sign is Layer 1: one entry per document with its ID, links and summary. The sample index is about 68 tokens.
• dist/canon-bundle.sign is Layer 2: the full text of every active document.
• dist/canon-manifest.json records the version, document count, build time and a SHA-256 hash, and canon-bundle.sign.sha256 lets you check the bundle has not changed.

Load the index into the prompt and serve documents through a tool.

The agent always sees the index, so it knows which documents exist and what each one covers. It calls a tool to fetch the full text only when a task needs it. This file works with any model or agent framework that supports tools; register get_canon_doc in whatever format yours uses.

import { readFileSync } from "node:fs";

const index = readFileSync("dist/canon-index.sign", "utf8");
const bundle = readFileSync("dist/canon-bundle.sign", "utf8");

// Split the Layer 2 bundle into documents, keyed by ID.
const docs = new Map();
for (const chunk of bundle.split(/^# --- .+ ---$/m)) {
  const id = chunk.match(/^@doc (\S+)/m)?.[1];
  if (id) docs.set(id, chunk.trim());
}

// Layer 1 goes into every system prompt.
export const systemPrompt = `You work under the following knowledge canon:
${index}
Call get_canon_doc with a document ID when you need its full rules.`;

// Layer 2 is served on demand through a tool.
export function get_canon_doc({ id }) {
  return docs.get(id) ?? `No active document with ID ${id}.`;
}

Ask the agent to issue a 700 dollar refund. It should see REFUND-001 in the index, fetch it, and ask for a support manager's approval.

Go further with the reference tools.

The sign-tools repository holds reference implementations at version 0.1.

Run sign-encode-repo on a small or sample repository first, so you can check its output before it touches your main codebase. If your security team needs to approve the tools, the team guide has a note you can send them.

To propose a new sigil or report a problem in the specification, open an issue on sign-lang before you write code. The contributing guide explains how proposals are reviewed.