Build Transaction

Overview

The build transaction endpoint constructs a Solana transaction from an Anchor IDL instruction definition. It handles argument encoding, account validation, and transaction serialization.

Endpoint

POST /api/:projectId/instructions/:name/build

Request Body

accounts

object

required

Map of account names to public keys (base58 format)

{
  "user": "7xKXtg2CW87d97TXJSDpbD5jBkheTqA83TZRuJosgAsU",
  "systemProgram": "11111111111111111111111111111111"
}

args

object

required

Map of argument names to values. Types are automatically encoded based on the IDL.Supported types:

Primitives: u8, u16, u32, u64, u128, i8, i16, i32, i64, i128, f32, f64, bool
Complex: string, publicKey, bytes
Collections: Vec<T>, [T; N] (fixed-size arrays)
Optional: Option<T>
Custom: Defined structs from IDL types

{
  "amount": 1000000,
  "recipient": "9xQeWvG816bUx9EPjHmaT23yvVM2ZWbrrpZb9PusVFin",
  "config": {
    "feeRate": 100,
    "enabled": true
  }
}

feePayer

string

required

Public key (base58) of the transaction fee payer

recentBlockhash

string

Optional recent blockhash. If not provided, it will be fetched from the RPC.

network

string

default:"mainnet"

Network to use for RPC calls:

"mainnet" or "mainnet-beta" - Solana mainnet
"devnet" - Solana devnet
Custom RPC URL (e.g., "https://api.custom-rpc.com")

Response

transaction

string

Base58-encoded serialized transaction message

message

string

Human-readable description of the transaction

accounts

array

List of accounts used in the instruction

Show Account Object

name

string

Account name from the IDL

pubkey

string

Public key (base58)

isSigner

boolean

Whether this account must sign the transaction

isWritable

boolean

Whether this account is writable

instruction

object

Detailed instruction information

Show Instruction Object

name

string

Instruction name

programId

string

Program ID (base58)

data

string

Hex-encoded instruction data (discriminator + encoded arguments)

accounts

array

Same as top-level accounts array

estimatedFee

number

Estimated transaction fee in lamports (typically 5000)

Example

curl -X POST https://api.orquestra.so/api/my-project/instructions/transfer/build \
  -H "Content-Type: application/json" \
  -d '{
    "accounts": {
      "from": "7xKXtg2CW87d97TXJSDpbD5jBkheTqA83TZRuJosgAsU",
      "to": "9xQeWvG816bUx9EPjHmaT23yvVM2ZWbrrpZb9PusVFin",
      "systemProgram": "11111111111111111111111111111111"
    },
    "args": {
      "amount": 1000000
    },
    "feePayer": "7xKXtg2CW87d97TXJSDpbD5jBkheTqA83TZRuJosgAsU",
    "network": "devnet"
  }'

Response Example

{
  "transaction": "3yZe7d4FVmqPGPKqRLdnKpC...",
  "message": "Transaction for my_program.transfer",
  "accounts": [
    {
      "name": "from",
      "pubkey": "7xKXtg2CW87d97TXJSDpbD5jBkheTqA83TZRuJosgAsU",
      "isSigner": true,
      "isWritable": true
    },
    {
      "name": "to",
      "pubkey": "9xQeWvG816bUx9EPjHmaT23yvVM2ZWbrrpZb9PusVFin",
      "isSigner": false,
      "isWritable": true
    },
    {
      "name": "systemProgram",
      "pubkey": "11111111111111111111111111111111",
      "isSigner": false,
      "isWritable": false
    }
  ],
  "instruction": {
    "name": "transfer",
    "programId": "TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA",
    "data": "a7b3c4d5e6f7890102030405060708091011121314151617181920",
    "accounts": [
      /* same as accounts array above */
    ]
  },
  "estimatedFee": 5000
}

Error Responses

400 Bad Request

Missing required fields (accounts, args, or feePayer)
Invalid build request (missing required accounts/arguments)
Invalid public key format

404 Not Found

Project not found or not public
Instruction not found in IDL

500 Internal Server Error

Failed to build transaction
RPC connection error

Validation

The endpoint performs the following validations:

Account Validation
- All required accounts must be provided
- Public keys must be valid base58 (32-44 characters)
- Unknown account names are rejected
Argument Validation
- All required arguments must be provided
- For defined types (structs), all fields must be present
- Type validation based on IDL definitions
Transaction Building
- Instruction discriminator: SHA-256 hash of "global:<instruction_name>" (first 8 bytes)
- Arguments encoded using Borsh serialization
- Recent blockhash fetched if not provided

Rate Limiting

This endpoint is rate-limited to prevent abuse. See Rate Limiting for details.

List Instructions - Get available instructions
Get Instruction Details - View instruction schema
Derive PDA - Calculate Program Derived Addresses

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