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POST
/
curl -X POST "https://starknet.paymaster.avnu.fi" \
  -H "Content-Type: application/json" \
  -H "x-paymaster-api-key: $PAYMASTER_API_KEY" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "paymaster_buildTransaction",
    "params": {
      "transaction": {
        "type": "apply_action",
        "apply_action": { "pool_address": "0x04c9...pool" }
      },
      "parameters": {
        "version": "0x1",
        "fee_mode": {
          "mode": "sponsored_private",
          "pool_fee_token": "0x04718f5a0fc34cc1af16a1cdee98ffb20c31f5cd61d6ab07201858f4287c938d",
          "tip": "normal"
        }
      }
    }
  }'

import { buildPrivateSwapFee, PRIVACY_POOL_ADDRESS } from '@avnu/avnu-sdk';

const fee = await buildPrivateSwapFee({
  poolAddress: PRIVACY_POOL_ADDRESS,
  feeMode: { poolFeeToken: STRK, tip: 'normal' },
  paymasterApiKey: PAYMASTER_API_KEY,
});
// { token, recipient, amount } — withdraw this inside the private transaction

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "type": "apply_action",
    "parameters": {
      "version": "0x1",
      "fee_mode": { "mode": "sponsored_private", "pool_fee_token": "0x04718...938d", "tip": "normal" }
    },
    "fee": {
      "gas_token_price_in_strk": "0xde0b6b3a7640000",
      "estimated_fee_in_strk": "0x2386f26fc10000",
      "estimated_fee_in_gas_token": "0x2386f26fc10000",
      "suggested_max_fee_in_strk": "0x354a6ba7a18000",
      "suggested_max_fee_in_gas_token": "0x354a6ba7a18000"
    },
    "fee_action": {
      "type": "withdraw",
      "recipient": "0x05f4...fee",
      "token": "0x04718...938d",
      "amount": "0x2386f26fc10000"
    }
  }
}

​
Overview

JSON-RPC method paymaster_buildTransaction with the apply_action type. Returns the fee estimate and the fee_action: the pool fee that must be withdrawn (inside the private transaction) to reimburse the paymaster. Use invoke_and_apply_action instead when a signed user call must be wrapped in the same transaction (e.g. an approve for a deposit) — the response then also contains the typed_data to sign. The endpoint is the base URL itself (no path): https://starknet.paymaster.avnu.fi (mainnet) or https://sepolia.paymaster.avnu.fi (testnet).

​
Headers

​
x-paymaster-api-key
string
required
Portal API key. Required for the sponsored fee modes (sponsored, sponsored_private)

​
Body (JSON-RPC 2.0)

​
method
string
required
paymaster_buildTransaction
​
params.transaction.type
string
required
apply_action, or invoke_and_apply_action when a signed user call is required
​
params.transaction.apply_action.pool_address
string
required
The privacy pool address. Must be the pool whitelisted by the paymaster (exported by the SDK as PRIVACY_POOL_ADDRESS / SEPOLIA_PRIVACY_POOL_ADDRESS)
​
params.transaction.invoke
object
Only for invoke_and_apply_action: { user_address, calls } — the user calls to wrap
​
params.parameters.version
string
required
0x1
​
params.parameters.fee_mode
object
required
{ mode: 'sponsored_private', pool_fee_token, tip? }. pool_fee_token is the token the pool fee is paid in; tip is slow | normal | fast (default normal)
​
params.parameters.time_bounds
object
Optional { execute_after, execute_before } (unix seconds)

​
Response

​
type
string
Echoes the transaction type
​
fee_action
object
required
The pool fee to withdraw inside the private transaction: { type: 'withdraw', recipient, token, amount } (hex amounts)
​
fee
object
Fee estimate: gas_token_price_in_strk, estimated_fee_in_strk, estimated_fee_in_gas_token, suggested_max_fee_in_strk, suggested_max_fee_in_gas_token (hex)
​
parameters
object
Echoes the execution parameters
​
typed_data
object
Only for invoke_and_apply_action: the SNIP-12 typed data the user must sign

​
Errors

CodeNameWhen
151TOKEN_NOT_SUPPORTEDpool_fee_token is not supported
156TRANSACTION_EXECUTION_ERRORExecution failure (including a non-whitelisted pool_address)
163UNKNOWN_ERRORInvalid API key, service unavailable, or blacklisted call
168SPONSORED_PRIVATE_REQUIRES_PRIVACYsponsored_private used with a non-private transaction type
curl -X POST "https://starknet.paymaster.avnu.fi" \
  -H "Content-Type: application/json" \
  -H "x-paymaster-api-key: $PAYMASTER_API_KEY" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "paymaster_buildTransaction",
    "params": {
      "transaction": {
        "type": "apply_action",
        "apply_action": { "pool_address": "0x04c9...pool" }
      },
      "parameters": {
        "version": "0x1",
        "fee_mode": {
          "mode": "sponsored_private",
          "pool_fee_token": "0x04718f5a0fc34cc1af16a1cdee98ffb20c31f5cd61d6ab07201858f4287c938d",
          "tip": "normal"
        }
      }
    }
  }'

import { buildPrivateSwapFee, PRIVACY_POOL_ADDRESS } from '@avnu/avnu-sdk';

const fee = await buildPrivateSwapFee({
  poolAddress: PRIVACY_POOL_ADDRESS,
  feeMode: { poolFeeToken: STRK, tip: 'normal' },
  paymasterApiKey: PAYMASTER_API_KEY,
});
// { token, recipient, amount } — withdraw this inside the private transaction

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "type": "apply_action",
    "parameters": {
      "version": "0x1",
      "fee_mode": { "mode": "sponsored_private", "pool_fee_token": "0x04718...938d", "tip": "normal" }
    },
    "fee": {
      "gas_token_price_in_strk": "0xde0b6b3a7640000",
      "estimated_fee_in_strk": "0x2386f26fc10000",
      "estimated_fee_in_gas_token": "0x2386f26fc10000",
      "suggested_max_fee_in_strk": "0x354a6ba7a18000",
      "suggested_max_fee_in_gas_token": "0x354a6ba7a18000"
    },
    "fee_action": {
      "type": "withdraw",
      "recipient": "0x05f4...fee",
      "token": "0x04718...938d",
      "amount": "0x2386f26fc10000"
    }
  }
}