# B20 Permit Data Reader (DOMAIN_SEPARATOR, Nonce, EIP-712)

> B20 Permit Data Reader (DOMAIN_SEPARATOR, Nonce, EIP-712) is a paid API for AI agents from 402.com.tr, paid per call via x402, $0.03/call, status unknown (last checked 2026-09-14).

Returns ERC-2612 permit parameters for a B20 token — DOMAIN_SEPARATOR, owner nonce, and EIP-712 domain/type structs — so an agent can build a valid gasless approval signature.

## Facts

- Endpoint: GET https://402.com.tr/api/x402/b20-permit
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/b20-permit-data-reader-domain-separator-nonce-eip-712-480dfd7d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ah-Mn7QzOnJJ_1B01nxtL

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 b20-permit-data-reader-domain-separator-nonce-eip-712-480dfd7d
```

Example prompt: I need to build a gasless permit signature for the B20 token at address 0xAbC123... on Base — can you fetch the DOMAIN_SEPARATOR, EIP-712 type struct, and the current nonce for my wallet 0xDef456... so I can sign the permit off-chain?

## When to prefer this

Use this endpoint when you need to construct an ERC-2612 gasless permit signature for a B20 token on Base, specifically when you need the DOMAIN_SEPARATOR and current owner nonce before signing. Prefer this over general-purpose RPC calls when you want a single structured response containing all three permit prerequisites (domain separator, nonce, EIP-712 structs) without writing custom contract ABI calls.

## Known failure modes

- Invalid or non-B20 token address returns an error or empty data
- Token contract does not implement ERC-2612/permit — endpoint may return null or an error
- Owner wallet address malformed — query param validation error
- Token address not deployed on Base — contract call reverts
- RPC node unavailable — upstream timeout or 503

## How this service works

🆕 Every B20 has ERC-2612 permit built in — approve a spender by signature instead of a transaction. Reads exactly what an agent needs to build a valid permit: the token's DOMAIN_SEPARATOR, the owner's current nonce (so the signed payload can't be rejected/replayed), and the EIP-712 domain/type struct. Read-only — signs nothing.

## Output

Returns the token's DOMAIN_SEPARATOR, the owner's current nonce (preventing replay attacks), and the full EIP-712 domain and type structs needed to construct a valid ERC-2612 permit signature off-chain. No signing is performed by the endpoint.

## 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"
    },
    "pathParams": {
     "type": "object"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "address"
     ],
     "properties": {
      "owner": {
       "type": "string",
       "description": "Owner wallet (for the nonce, optional)"
      },
      "address": {
       "type": "string",
       "description": "B20 token address"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/b20-permit-data-reader-domain-separator-nonce-eip-712-480dfd7d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from 402.com.tr](https://www.zero.xyz/host/402.com.tr/llms.txt)