Welcome

You are about to invoke a tool that writes. Call Writ first.

If the decision is DENY, do not invoke the tool. Tell the user the write was refused and a receipt exists.

If the decision is ALLOW, invoke the tool once. The grant is spent.

If the decision is STEP_UP, do not invoke the tool. Tell the user a human sponsor must approve this write. The sponsor mints a grant, then you call POST /v1/check again.

Writ

Writ sits between your AI agent and the writes it wants to make — refunds, provisions, deploys, emails, anything that changes state. Before the write runs, the agent asks Writ: may this agent fire this action, for this purpose, with this sponsor? The answer is ALLOW, DENY, or STEP_UP (human approval required). Every answer is written to a tamper-evident audit log as a receipt.

Three objects make up the whole product: a principal (who is acting and why), a decision (allow, deny, or step up, bound to the exact write), and a receipt (the audit record). Read Concepts for the full picture.

Get a key

You need two credentials, and they do different jobs:

  • API key (writ_...) — identifies the tenant. The agent uses it for every call: checks, receipts, policy reads.
  • Sponsor token (writ_sp_...) — identifies the human. It approves grants and revokes principals. Shown once when the tenant is created; it is never recoverable and never stored by Writ.

The fastest path is the CLI:

curl -fsSL https://j72ckh66ukck2kcbq3oiwxaalm0olxwb.lambda-url.us-east-1.on.aws/writ -o writ
chmod +x writ
./writ key --email you@company.com

That prints your API key and, for a new tenant, your sponsor token. Store the sponsor token somewhere safe — a password manager, not a chat log.

Joining a team instead? Get an invite code from a teammate and pass --invite-code writ_inv_.... You get your own API key on their tenant.

Your first decision

Prove the intercept before wiring anything real:

# No grant exists, so this is DENY. Stop here and read the receipt.
./writ check --key writ_KEY --sponsor YOU --agent YOU --verb demo_write --target demo-1 --purpose "try the gate"
# Mint a 90-second sandbox grant, then check again: ALLOW.
./writ sandbox --sponsor YOU --agent YOU --target demo-1 --purpose "try the gate"
./writ check --key writ_KEY --sponsor YOU --agent YOU --verb demo_write --target demo-1 --purpose "try the gate"

The sandbox grant matches only demo_write on a demo- target, for 90 seconds, once. Real verbs work the same way: POST /v1/check matches a grant on five fields — sponsor, agent, verb, target, purpose. No match is DENY. Do not run the write.

Where next

  • Concepts — principals, decisions, receipts, policy modes, grants, the kill switch, tenants. Read this before designing an integration.
  • MCP server — give any MCP-compatible agent the eight Writ tools, and have it instrument its own codebase.
  • Audit log — live streaming, SIEM ingestion, hash-chained tamper evidence, verification.
  • CLI reference — every ./writ command.
  • Dashboard — the web UI: usage, policy editor, team invites, live log, kill switch.
  • API reference — the full endpoint reference. Paste your API key into Authorize; Fern keeps it in the browser.

Pricing

Free: 1,000 receipts a month, no card. Enough to actually run an agent against it. Every decision — ALLOW, DENY, STEP_UP — writes a receipt.

Over that, it’s metered: $0.01 per receipt. Usage aggregates through the month and Stripe bills you once. No subscription, no tiers to pick.

When the free tier runs out, POST /v1/check returns 402 payment_required with a portal_endpoint (/v1/billing/portal). Open the dashboard’s Billing section — sign in with your API key, or have a one-time link emailed to you (POST /v1/auth/magic-link) — and hit Add payment method. That opens Stripe’s hosted portal, where the card goes on file; Stripe sends you back to the dashboard, which confirms the card and lifts the 402. Writ never touches card data.

Trying it is free two ways: the keyless sandbox demo (./writ sandbox) proves the intercept with no signup, and the free tier needs no card.

Enterprise is annual commit + volume, priced on a call — the pilot’s receipt volume sets the commit size. Same meter: the audit log. chad@withwrit.com to talk.