Contract storage slot

Read one 32-byte storage slot from a contract, the raw state under whatever the source code calls it. Send GET /api/chain/storage with the required fields address and slot and pay $0.001 per call over x402 or MPP (there is no free tier). It returns a JSON object with address, network, slot, block, value and 3 more.

Returns the word as hex plus three readings of the same bytes - unsigned integer, address (low 20 bytes) and boolean - because a slot is untyped on chain and only the caller knows which it meant. Useful for proxy implementation slots, paused flags and any value the ABI does not expose. EVM chains: ethereum, base, polygon, arbitrum, optimism.

Category: Crypto & onchain data · Tags: evm storage slot rpc contract · Also found as: eth_getStorageAt storage-at slot

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Parameters

Example request

curl -i "https://agent402.tools/api/chain/storage?address=0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913&slot=0x0&network=base"

Without payment this returns HTTP 402 Payment Required with the exact price for chain-storage; any x402 v2 or MPP client pays it and retries.

Example response

{
  "address": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
  "network": "base",
  "slot": "0x0",
  "block": "latest",
  "value": "0x0000000000000000000000000000000000000000000000000000000000000001",
  "asUint": "1",
  "asAddress": "0x0000000000000000000000000000000000000001",
  "asBool": true
}

From an MCP client

catalog.call {
  "slug": "chain-storage",
  "params": {
    "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "slot": "0x0",
    "network": "base"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for chain-storage; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• address and slot are required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• A POST with a JSON body to /api/chain/storage is served as this GET, with the body as the input.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

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();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/chain/storage?address=0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913&slot=0x0&network=base");

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