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Solidity Mapping Storage Slot Calculator
x402
Solidity Mapping Storage Slot Calculator is a paid API for AI agents from twin.unykorn.org, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-02).
Computes the EVM storage slot for a Solidity mapping entry given a key, base slot, and key type
Price / call$0.002
Success—
StatusUnknown
How this service works
Compute the storage slot of a Solidity mapping entry — Genesis402 / UnyKorn Operator Network
Output
Returns a JSON object with ok=true, the computed storage slot value (keccak256-derived EVM slot), the computation type identifier, and a payment receipt including transaction hash, amount paid in USD, and a unique receipt ID.
Example use cases
Debug contract storage state directly
“I'm debugging a Solidity contract and need to read the raw storage value for mapping(address => uint256) at base slot 2, for key 0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe with keyType address — what's the storage slot?”
Verify allowance mapping slot for ERC20 audit
“For a smart contract audit, I need to verify the storage slot of a nested mapping — outer key is 0xABCDEF0123456789 at base slot 5, keyType is uint256. Can you compute that storage slot?”
Automate state inspection in CI pipeline
“Our test pipeline needs to check contract state after each deploy — can you calculate the storage slot for mapping key 0x1234567890abcdef at slot 0, keyType address, so we can call eth_getStorageAt to verify the value?”
Technical details
Endpoint
POSThttps://twin.unykorn.org/storage-slot-mapping?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to programmatically compute the exact EVM storage slot for a Solidity mapping entry to use with eth_getStorageAt or similar low-level storage reads. Prefer this over manual keccak256 computation when building agents, debuggers, audit tools, or CI pipelines that need reliable, on-demand slot derivation without setting up a local Solidity/ethers.js environment.
Side effects
- Missing or invalid key parameter returns an error response
- Slot index below 0 (minimum 0) causes schema validation failure
- Unsupported or misspelled keyType may produce incorrect slot computation or error
- Network/payment failure returns non-ok response without slot result
- Malformed hex key string may cause computation error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| params | object |
Output
Schema · Response
{
"type": "json",
"example": {
"ok": true,
"type": "storage-slot-mapping",
"receipt": {
"tx_hash": "0x<64hex>",
"amount_usd": 0.002,
"receipt_id": "g402-<16hex>"
},
"generated_at": "<iso8601>"
}
}Tags
x402
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