Calculate maximum sendable ADA
curl --request POST \
--url https://nexus.gerowallet.io/api/tx/max-ada \
--header 'Content-Type: application/json' \
--header 'X-Api-Key: <api-key>' \
--data '
{
"outputs": [
{
"address": "<string>",
"lovelace": "<string>",
"assets": [
{
"policyId": "<string>",
"assetName": "<string>",
"quantity": "<string>"
}
]
}
],
"changeAddress": "<string>",
"utxos": [
{
"txHash": "<string>",
"address": "<string>",
"lovelace": "<string>",
"outputIndex": 1,
"assets": [
{
"policyId": "<string>",
"assetName": "<string>",
"quantity": "<string>"
}
],
"dataHash": "<string>",
"inlineDatum": "<string>",
"referenceScriptHash": "<string>"
}
],
"senderAddress": "<string>",
"ttl": 123,
"withdrawals": [
{
"stakeAddress": "<string>",
"amount": "<string>"
}
]
}
'import requests
url = "https://nexus.gerowallet.io/api/tx/max-ada"
payload = {
"outputs": [
{
"address": "<string>",
"lovelace": "<string>",
"assets": [
{
"policyId": "<string>",
"assetName": "<string>",
"quantity": "<string>"
}
]
}
],
"changeAddress": "<string>",
"utxos": [
{
"txHash": "<string>",
"address": "<string>",
"lovelace": "<string>",
"outputIndex": 1,
"assets": [
{
"policyId": "<string>",
"assetName": "<string>",
"quantity": "<string>"
}
],
"dataHash": "<string>",
"inlineDatum": "<string>",
"referenceScriptHash": "<string>"
}
],
"senderAddress": "<string>",
"ttl": 123,
"withdrawals": [
{
"stakeAddress": "<string>",
"amount": "<string>"
}
]
}
headers = {
"X-Api-Key": "<api-key>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {'X-Api-Key': '<api-key>', 'Content-Type': 'application/json'},
body: JSON.stringify({
outputs: [
{
address: '<string>',
lovelace: '<string>',
assets: [{policyId: '<string>', assetName: '<string>', quantity: '<string>'}]
}
],
changeAddress: '<string>',
utxos: [
{
txHash: '<string>',
address: '<string>',
lovelace: '<string>',
outputIndex: 1,
assets: [{policyId: '<string>', assetName: '<string>', quantity: '<string>'}],
dataHash: '<string>',
inlineDatum: '<string>',
referenceScriptHash: '<string>'
}
],
senderAddress: '<string>',
ttl: 123,
withdrawals: [{stakeAddress: '<string>', amount: '<string>'}]
})
};
fetch('https://nexus.gerowallet.io/api/tx/max-ada', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://nexus.gerowallet.io/api/tx/max-ada",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'outputs' => [
[
'address' => '<string>',
'lovelace' => '<string>',
'assets' => [
[
'policyId' => '<string>',
'assetName' => '<string>',
'quantity' => '<string>'
]
]
]
],
'changeAddress' => '<string>',
'utxos' => [
[
'txHash' => '<string>',
'address' => '<string>',
'lovelace' => '<string>',
'outputIndex' => 1,
'assets' => [
[
'policyId' => '<string>',
'assetName' => '<string>',
'quantity' => '<string>'
]
],
'dataHash' => '<string>',
'inlineDatum' => '<string>',
'referenceScriptHash' => '<string>'
]
],
'senderAddress' => '<string>',
'ttl' => 123,
'withdrawals' => [
[
'stakeAddress' => '<string>',
'amount' => '<string>'
]
]
]),
CURLOPT_HTTPHEADER => [
"Content-Type: application/json",
"X-Api-Key: <api-key>"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://nexus.gerowallet.io/api/tx/max-ada"
payload := strings.NewReader("{\n \"outputs\": [\n {\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ]\n }\n ],\n \"changeAddress\": \"<string>\",\n \"utxos\": [\n {\n \"txHash\": \"<string>\",\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"outputIndex\": 1,\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ],\n \"dataHash\": \"<string>\",\n \"inlineDatum\": \"<string>\",\n \"referenceScriptHash\": \"<string>\"\n }\n ],\n \"senderAddress\": \"<string>\",\n \"ttl\": 123,\n \"withdrawals\": [\n {\n \"stakeAddress\": \"<string>\",\n \"amount\": \"<string>\"\n }\n ]\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("X-Api-Key", "<api-key>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://nexus.gerowallet.io/api/tx/max-ada")
.header("X-Api-Key", "<api-key>")
.header("Content-Type", "application/json")
.body("{\n \"outputs\": [\n {\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ]\n }\n ],\n \"changeAddress\": \"<string>\",\n \"utxos\": [\n {\n \"txHash\": \"<string>\",\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"outputIndex\": 1,\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ],\n \"dataHash\": \"<string>\",\n \"inlineDatum\": \"<string>\",\n \"referenceScriptHash\": \"<string>\"\n }\n ],\n \"senderAddress\": \"<string>\",\n \"ttl\": 123,\n \"withdrawals\": [\n {\n \"stakeAddress\": \"<string>\",\n \"amount\": \"<string>\"\n }\n ]\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://nexus.gerowallet.io/api/tx/max-ada")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["X-Api-Key"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"outputs\": [\n {\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ]\n }\n ],\n \"changeAddress\": \"<string>\",\n \"utxos\": [\n {\n \"txHash\": \"<string>\",\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"outputIndex\": 1,\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ],\n \"dataHash\": \"<string>\",\n \"inlineDatum\": \"<string>\",\n \"referenceScriptHash\": \"<string>\"\n }\n ],\n \"senderAddress\": \"<string>\",\n \"ttl\": 123,\n \"withdrawals\": [\n {\n \"stakeAddress\": \"<string>\",\n \"amount\": \"<string>\"\n }\n ]\n}"
response = http.request(request)
puts response.read_body""{
"error": "No UTXOs available"
}{
"error": "Internal server error"
}Transaction Builder
Calculate maximum sendable ADA
Computes the maximum ADA that can be sent to a destination address by selecting all available UTxOs, estimating the transaction fee, and accounting for a change output min-UTxO when native tokens are present. Returns max_lovelace = total_balance - estimated_fee - change_min_utxo. Either provide UTXOs directly or a sender address to fetch UTXOs from the network.
POST
/
api
/
tx
/
max-ada
Calculate maximum sendable ADA
curl --request POST \
--url https://nexus.gerowallet.io/api/tx/max-ada \
--header 'Content-Type: application/json' \
--header 'X-Api-Key: <api-key>' \
--data '
{
"outputs": [
{
"address": "<string>",
"lovelace": "<string>",
"assets": [
{
"policyId": "<string>",
"assetName": "<string>",
"quantity": "<string>"
}
]
}
],
"changeAddress": "<string>",
"utxos": [
{
"txHash": "<string>",
"address": "<string>",
"lovelace": "<string>",
"outputIndex": 1,
"assets": [
{
"policyId": "<string>",
"assetName": "<string>",
"quantity": "<string>"
}
],
"dataHash": "<string>",
"inlineDatum": "<string>",
"referenceScriptHash": "<string>"
}
],
"senderAddress": "<string>",
"ttl": 123,
"withdrawals": [
{
"stakeAddress": "<string>",
"amount": "<string>"
}
]
}
'import requests
url = "https://nexus.gerowallet.io/api/tx/max-ada"
payload = {
"outputs": [
{
"address": "<string>",
"lovelace": "<string>",
"assets": [
{
"policyId": "<string>",
"assetName": "<string>",
"quantity": "<string>"
}
]
}
],
"changeAddress": "<string>",
"utxos": [
{
"txHash": "<string>",
"address": "<string>",
"lovelace": "<string>",
"outputIndex": 1,
"assets": [
{
"policyId": "<string>",
"assetName": "<string>",
"quantity": "<string>"
}
],
"dataHash": "<string>",
"inlineDatum": "<string>",
"referenceScriptHash": "<string>"
}
],
"senderAddress": "<string>",
"ttl": 123,
"withdrawals": [
{
"stakeAddress": "<string>",
"amount": "<string>"
}
]
}
headers = {
"X-Api-Key": "<api-key>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {'X-Api-Key': '<api-key>', 'Content-Type': 'application/json'},
body: JSON.stringify({
outputs: [
{
address: '<string>',
lovelace: '<string>',
assets: [{policyId: '<string>', assetName: '<string>', quantity: '<string>'}]
}
],
changeAddress: '<string>',
utxos: [
{
txHash: '<string>',
address: '<string>',
lovelace: '<string>',
outputIndex: 1,
assets: [{policyId: '<string>', assetName: '<string>', quantity: '<string>'}],
dataHash: '<string>',
inlineDatum: '<string>',
referenceScriptHash: '<string>'
}
],
senderAddress: '<string>',
ttl: 123,
withdrawals: [{stakeAddress: '<string>', amount: '<string>'}]
})
};
fetch('https://nexus.gerowallet.io/api/tx/max-ada', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://nexus.gerowallet.io/api/tx/max-ada",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'outputs' => [
[
'address' => '<string>',
'lovelace' => '<string>',
'assets' => [
[
'policyId' => '<string>',
'assetName' => '<string>',
'quantity' => '<string>'
]
]
]
],
'changeAddress' => '<string>',
'utxos' => [
[
'txHash' => '<string>',
'address' => '<string>',
'lovelace' => '<string>',
'outputIndex' => 1,
'assets' => [
[
'policyId' => '<string>',
'assetName' => '<string>',
'quantity' => '<string>'
]
],
'dataHash' => '<string>',
'inlineDatum' => '<string>',
'referenceScriptHash' => '<string>'
]
],
'senderAddress' => '<string>',
'ttl' => 123,
'withdrawals' => [
[
'stakeAddress' => '<string>',
'amount' => '<string>'
]
]
]),
CURLOPT_HTTPHEADER => [
"Content-Type: application/json",
"X-Api-Key: <api-key>"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://nexus.gerowallet.io/api/tx/max-ada"
payload := strings.NewReader("{\n \"outputs\": [\n {\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ]\n }\n ],\n \"changeAddress\": \"<string>\",\n \"utxos\": [\n {\n \"txHash\": \"<string>\",\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"outputIndex\": 1,\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ],\n \"dataHash\": \"<string>\",\n \"inlineDatum\": \"<string>\",\n \"referenceScriptHash\": \"<string>\"\n }\n ],\n \"senderAddress\": \"<string>\",\n \"ttl\": 123,\n \"withdrawals\": [\n {\n \"stakeAddress\": \"<string>\",\n \"amount\": \"<string>\"\n }\n ]\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("X-Api-Key", "<api-key>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://nexus.gerowallet.io/api/tx/max-ada")
.header("X-Api-Key", "<api-key>")
.header("Content-Type", "application/json")
.body("{\n \"outputs\": [\n {\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ]\n }\n ],\n \"changeAddress\": \"<string>\",\n \"utxos\": [\n {\n \"txHash\": \"<string>\",\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"outputIndex\": 1,\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ],\n \"dataHash\": \"<string>\",\n \"inlineDatum\": \"<string>\",\n \"referenceScriptHash\": \"<string>\"\n }\n ],\n \"senderAddress\": \"<string>\",\n \"ttl\": 123,\n \"withdrawals\": [\n {\n \"stakeAddress\": \"<string>\",\n \"amount\": \"<string>\"\n }\n ]\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://nexus.gerowallet.io/api/tx/max-ada")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["X-Api-Key"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"outputs\": [\n {\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ]\n }\n ],\n \"changeAddress\": \"<string>\",\n \"utxos\": [\n {\n \"txHash\": \"<string>\",\n \"address\": \"<string>\",\n \"lovelace\": \"<string>\",\n \"outputIndex\": 1,\n \"assets\": [\n {\n \"policyId\": \"<string>\",\n \"assetName\": \"<string>\",\n \"quantity\": \"<string>\"\n }\n ],\n \"dataHash\": \"<string>\",\n \"inlineDatum\": \"<string>\",\n \"referenceScriptHash\": \"<string>\"\n }\n ],\n \"senderAddress\": \"<string>\",\n \"ttl\": 123,\n \"withdrawals\": [\n {\n \"stakeAddress\": \"<string>\",\n \"amount\": \"<string>\"\n }\n ]\n}"
response = http.request(request)
puts response.read_body""{
"error": "No UTXOs available"
}{
"error": "Internal server error"
}Authorizations
apiKeyAuthbearerAuth
API key (programmatic access — recommended)
Send your API key in the X-Api-Key header. Keys start with nxs_ and are
created in the dashboard (or via POST /api/keys with a session JWT).
Each key is scoped to one chain and one network (for example
cardano-mainnet), fixed at creation time. It cannot query a different network
on the same chain, and it cannot query a different chain at all. A mismatched
network parameter returns 400 Network Mismatch. Create one key per chain
and network under the same account.
This is the credential most integrations should use.
Query Parameters
Available options:
CARDANO_MAINNET, CARDANO_PREPROD, CARDANO_PREVIEW, APEX_PRIME_MAINNET, APEX_VECTOR_MAINNET, APEX_VECTOR_TESTNET, MIDNIGHT_MAINNET, MIDNIGHT_PREPROD, MIDNIGHT_PREVIEW, BITCOIN_MAINNET, BITCOIN_TESTNET4 Body
application/json
Maximum array length:
50Show child attributes
Show child attributes
Maximum string length:
256Maximum array length:
200Show child attributes
Show child attributes
Available options:
CARDANO_MAINNET, CARDANO_PREPROD, CARDANO_PREVIEW, APEX_PRIME_MAINNET, APEX_VECTOR_MAINNET, APEX_VECTOR_TESTNET, MIDNIGHT_MAINNET, MIDNIGHT_PREPROD, MIDNIGHT_PREVIEW, BITCOIN_MAINNET, BITCOIN_TESTNET4 Maximum array length:
10Show child attributes
Show child attributes
⌘I