Writ is a deterministic settlement engine: agents pay under policy with exactly-once settlement, every payment leaves a receipt, and the whole ledger replays for anyone to audit. No human in the loop — and no way for an agent to spend outside its rules.
An agent that retries on timeout, or runs concurrently with copies of itself, settles once — not twice. Proven, not best-effort.
An agent hands a narrower budget to a sub-agent, which hands a tighter one to its own — cryptographically unable to widen. No card can branch authority.
Hold a payment against a signed delivery promise. Provider delivers something else? Deterministic refund, no human, no dispute queue.
The ledger is append-only and hash-chained; its head is published and signed. Record it and hold us to it — we hand you the tools to catch us.
On 16 September 2026 an agent paid $1 USDC through Writ, settled on Solana mainnet. Just before it, Writ refused a $5 attempt over the agent's $1 limit; a refusal moves nothing, so only the $1 is on chain. A capped test with our own funds.
Open a receipt from this server and verify its Ed25519 signature in your own browser, against the key we publish. The page never asks us whether the receipt is valid — and there is a button on it that alters one field so you can watch the check fail.
The signed head of this server's ledger, published so a rewrite of history collides with what you recorded.
A validator that does not run the payment engine signs this head with its own key. If its head ever disagrees with the one above, this panel says so — it never claims safe on a head we don't publish.
Writ is in a controlled pilot on devnet. Leave an email and what you would point an agent at, and you get an invite with a funded sandbox agent and a spending policy you set. No card, no call.
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One URL. Your agent joins a sandbox, pays under a budget it cannot exceed, is refused when it tries to overspend, and replays the ledger to check the balances itself.
https://writ.money/mcpCustomize → Connectors → + → Add custom connector, then paste the URL.
claude mcp add --transport http writ https://writ.money/mcp
Add to ~/.cursor/mcp.json:
{ "mcpServers": { "writ": { "url": "https://writ.money/mcp" } } }
“Join the Writ sandbox, pay $1 for an API call, try to pay $100, then verify the ledger.”