# On-Chain Storage Slot Reader

> On-Chain Storage Slot Reader is a paid API for AI agents from x402-agent-store.rileycraig14.workers.dev, paid per call via x402, $0.09/call, status unknown (last checked 2026-09-16).

Reads a specific storage slot value from a smart contract on EVM-compatible chains (Base, Ethereum, Optimism, Arbitrum, Polygon, Gnosis)

## Facts

- Endpoint: GET https://x402-agent-store.rileycraig14.workers.dev/chain/storage
- Price: $0.09/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/on-chain-storage-slot-reader-3443a001
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_pNfT2A9dWDA_0XRNIVgAd

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability on-chain-storage-slot-reader-3443a001
```

Example prompt: What's stored at storage slot 0x0 of the contract 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48 on Ethereum?

## When to prefer this

Use this endpoint when you need low-level raw storage reads from EVM smart contracts without requiring an ABI, especially across multiple chains (Base, Ethereum, Optimism, Arbitrum, Polygon, Gnosis). Prefer it over ethers.js or direct RPC calls when you want a pay-per-use, keyless HTTP interface that accepts USDC via x402. Ideal for agents that need to inspect contract internals, verify upgrade proxy slots, or read packed storage values programmatically.

## Known failure modes

- Invalid contract address format returns an error
- Storage slot not found or unoccupied returns 0x000...000
- Unsupported chain name returns a validation error
- Malformed hex slot value may cause a parse error
- Network RPC unavailability causes a timeout or 5xx error
- Payment failure via x402 prevents the call from being processed

## How this service works

Read any raw contract storage slot via eth_getStorageAt — the low-level read auditing, proxy-resolution and advanced trading agents make to inspect contract state directly. Pass address + slot. Across Base, Ethereum, Optimism, Arbitrum, Polygon, Gnosis. Free public RPC; undercuts onesource at $0.001 on 6 chains.

## Output

Returns a JSON object containing the queried contract address, chain name, storage slot index, and the raw 32-byte hex value stored at that slot on the specified EVM chain.

## Example request

```json
{
 "input": {
  "type": "http",
  "method": "GET",
  "output": {
   "type": "object"
  },
  "queryParams": {
   "slot": "0x0",
   "chain": "ethereum",
   "address": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
  }
 }
}
```

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "address",
      "slot"
     ],
     "properties": {
      "slot": {
       "type": "string",
       "description": "Storage slot, hex or decimal"
      },
      "chain": {
       "type": "string",
       "description": "base|ethereum|optimism|arbitrum|polygon|gnosis (default base)"
      },
      "address": {
       "type": "string",
       "description": "Contract address (0x...)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "value": {
       "type": "string"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "slot": "0x0",
  "chain": "ethereum",
  "value": "0x0000...0001",
  "address": "0x..."
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/on-chain-storage-slot-reader-3443a001/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-agent-store.rileycraig14.workers.dev](https://www.zero.xyz/host/x402-agent-store.rileycraig14.workers.dev/llms.txt)