Memory compare-and-set

Atomically write (or release) a key only if its current value equals `expected` — the coordination primitive for distributed locks and optimistic concurrency across agents. Acquire a lock: expected=null + a value + ttlSeconds. Release it: expected=<your token> with no value (deletes on match). Update safely: expected=<old>, value=<new>. Returns whether it swapped and the current value.

Input

Field	Type	Description
key *	string	Key to conditionally write
expected	any	Required current value to match (null or omitted = key absent/expired)
value	any	New value to set on match; omit to DELETE on match (lock release)
ttlSeconds	number	Optional TTL for the written value (lease for locks)
owner	string	Optional 0x namespace (requires a readwrite grant)

Example output

{
  "key": "locks/import",
  "swapped": true,
  "value": "agent-7",
  "owner": "0x…",
  "expiresAt": 1760086430
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/memory/cas \
  -H "Content-Type: application/json" \
  -d '{"key":"locks/import","expected":null,"value":"agent-7","ttlSeconds":30}'

The response is HTTP 402 Payment Required with exact payment requirements. Any x402 v2 client pays automatically and retries:

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/memory/cas", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "key": "locks/import",
    "expected": null,
    "value": "agent-7",
    "ttlSeconds": 30
  }),
});

Wallet-only. This tool reaches the network/browser/storage, so it is paid in USDC via x402 (no proof-of-work tier).

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