user124525: I am new to Bitcoin and Blockchain, and Blockcypher..
I am trying to use Blockcypher APIs to create (and sign) and send a transaction (on testnet). The request i provide has 1 input and 1 output, but the response i receive has 2 inputs/outputs/tosign 50% of the time.. Why would this be? Thanks
Sample Request:
Posting to https://api.blockcypher.com/v1/btc/test3/txs/new?token=XXXXXXXX
{
    "double_spend": false,
    "inputs": [{
        "addresses": ["mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD"]
    }],
    "outputs": [{
        "value": 2,
        "addresses": ["tb1qfefhgu4npfqjk36v66eqk6ee0gska720j09nvr"]
    }]
}

Response:
{
    "tx": {
        "hash": "b520ccb4b9ab96075c3cf1a91b0c7710a22332f0bb4d25409bcf9693a35477dd",
        "block_height": -1,
        "addresses": ["mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD", "tb1qfefhgu4npfqjk36v66eqk6ee0gska720j09nvr"],
        "total": 55000,
        "fees": 30000,
        "relayed_by": "35.226.46.118",
        "received": "2021-07-22T10:19:47.853381661Z",
        "ver": 1,
        "vin_sz": 2,
        "vout_sz": 2,
        "confirmations": 0,
        "preference": "high",
        "double_spend": false,
        "inputs": [{
            "prev_hash": "34e749b34cc75b996e7b28638cc4648958942b046bf9961837af7ab0046e53d1",
            "output_index": 0,
            "output_value": 10000,
            "addresses": ["mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD"],
            "script_type": "pay-to-pubkey-hash"
        }, {
            "prev_hash": "106ad632e2474e683b2180181c1b911bc4d5727db5ab341ee8aded3b78fb2da7",
            "output_index": 1,
            "output_value": 75000,
            "addresses": ["mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD"],
            "script_type": "pay-to-pubkey-hash"
        }],
        "outputs": [{
            "value": 2,
            "script": "00144e537472b30a412b474cd6b20b6b397a216ef94f",
            "addresses": ["tb1qfefhgu4npfqjk36v66eqk6ee0gska720j09nvr"],
            "script_type": "pay-to-witness-pubkey-hash"
        }, {
            "value": 54998,
            "script": "76a91471b6e0ce39475cbe5cd43966f5c7eb80a886952088ac",
            "addresses": ["mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD"],
            "script_type": "pay-to-pubkey-hash"
        }]
    },
    "tosign": ["c0859bbf0f964af14c01d9ff2da9e5254279d02c5c75c902e3a8180db6bb67e5", "91a6c5b3003047c0af81348f12867918ebc4efd70f3ff1a5ee9e4566bf361de8"],
    "signatures": [],
    "pubkeys": []
}

Thanks

user13866: 
Not sure what other amounts relate to.

    "total": 55000,

The amount being transferred to outputs in this transaction
    "fees": 30000,

The difference between total input amounts  and total output amounts.
Note that the above two values sum to 85000.
        "output_value": 10000,

An amount associated with one UTXO with the specified spending address
        "output_value": 75000,

An amount associated with a second UTXO with the specified spending address
Note that the above two values sum to 85000.
        "value": 2,

The amount you specified be sent to the destination address
        "value": 54998,

The remainder of the 55000 ("total", see above) being returned as change.

124525: <p>I am new to Bitcoin and Blockchain, and Blockcypher..</p>
<p>I am trying to use Blockcypher APIs to create (and sign) and send a transaction (on testnet). The request i provide has 1 input and 1 output, but the response i receive has <strong>2</strong> inputs/outputs/tosign 50% of the time.. Why would this be? Thanks</p>
<p>Sample Request:</p>
<p>Posting to <a href="https://api.blockcypher.com/v1/btc/test3/txs/new?token=XXXXXXXX" rel="nofollow noreferrer">https://api.blockcypher.com/v1/btc/test3/txs/new?token=XXXXXXXX</a></p>
<pre><code>{
    &quot;double_spend&quot;: false,
    &quot;inputs&quot;: [{
        &quot;addresses&quot;: [&quot;mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD&quot;]
    }],
    &quot;outputs&quot;: [{
        &quot;value&quot;: 2,
        &quot;addresses&quot;: [&quot;tb1qfefhgu4npfqjk36v66eqk6ee0gska720j09nvr&quot;]
    }]
}
</code></pre>
<p>Response:</p>
<pre><code>{
    &quot;tx&quot;: {
        &quot;hash&quot;: &quot;b520ccb4b9ab96075c3cf1a91b0c7710a22332f0bb4d25409bcf9693a35477dd&quot;,
        &quot;block_height&quot;: -1,
        &quot;addresses&quot;: [&quot;mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD&quot;, &quot;tb1qfefhgu4npfqjk36v66eqk6ee0gska720j09nvr&quot;],
        &quot;total&quot;: 55000,
        &quot;fees&quot;: 30000,
        &quot;relayed_by&quot;: &quot;35.226.46.118&quot;,
        &quot;received&quot;: &quot;2021-07-22T10:19:47.853381661Z&quot;,
        &quot;ver&quot;: 1,
        &quot;vin_sz&quot;: 2,
        &quot;vout_sz&quot;: 2,
        &quot;confirmations&quot;: 0,
        &quot;preference&quot;: &quot;high&quot;,
        &quot;double_spend&quot;: false,
        &quot;inputs&quot;: [{
            &quot;prev_hash&quot;: &quot;34e749b34cc75b996e7b28638cc4648958942b046bf9961837af7ab0046e53d1&quot;,
            &quot;output_index&quot;: 0,
            &quot;output_value&quot;: 10000,
            &quot;addresses&quot;: [&quot;mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD&quot;],
            &quot;script_type&quot;: &quot;pay-to-pubkey-hash&quot;
        }, {
            &quot;prev_hash&quot;: &quot;106ad632e2474e683b2180181c1b911bc4d5727db5ab341ee8aded3b78fb2da7&quot;,
            &quot;output_index&quot;: 1,
            &quot;output_value&quot;: 75000,
            &quot;addresses&quot;: [&quot;mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD&quot;],
            &quot;script_type&quot;: &quot;pay-to-pubkey-hash&quot;
        }],
        &quot;outputs&quot;: [{
            &quot;value&quot;: 2,
            &quot;script&quot;: &quot;00144e537472b30a412b474cd6b20b6b397a216ef94f&quot;,
            &quot;addresses&quot;: [&quot;tb1qfefhgu4npfqjk36v66eqk6ee0gska720j09nvr&quot;],
            &quot;script_type&quot;: &quot;pay-to-witness-pubkey-hash&quot;
        }, {
            &quot;value&quot;: 54998,
            &quot;script&quot;: &quot;76a91471b6e0ce39475cbe5cd43966f5c7eb80a886952088ac&quot;,
            &quot;addresses&quot;: [&quot;mqtDjKw8wCyPBvk61NfkgmNFZDwHvCJTUD&quot;],
            &quot;script_type&quot;: &quot;pay-to-pubkey-hash&quot;
        }]
    },
    &quot;tosign&quot;: [&quot;c0859bbf0f964af14c01d9ff2da9e5254279d02c5c75c902e3a8180db6bb67e5&quot;, &quot;91a6c5b3003047c0af81348f12867918ebc4efd70f3ff1a5ee9e4566bf361de8&quot;],
    &quot;signatures&quot;: [],
    &quot;pubkeys&quot;: []
}
</code></pre>
<p>Thanks</p>
 13866: <blockquote>
<p><strong>Not sure what other amounts relate to.</strong></p>
</blockquote>
<pre><code>    &quot;total&quot;: 55000,
</code></pre>
<p>The amount being transferred to outputs in this transaction</p>
<pre><code>    &quot;fees&quot;: 30000,
</code></pre>
<p>The difference between total input amounts  and total output amounts.</p>
<p>Note that the above two values sum to 85000.</p>
<pre><code>        &quot;output_value&quot;: 10000,
</code></pre>
<p>An amount associated with one UTXO with the specified spending address</p>
<pre><code>        &quot;output_value&quot;: 75000,
</code></pre>
<p>An amount associated with a second UTXO with the specified spending address</p>
<p>Note that the above two values sum to 85000.</p>
<pre><code>        &quot;value&quot;: 2,
</code></pre>
<p>The amount you specified be sent to the destination address</p>
<pre><code>        &quot;value&quot;: 54998,
</code></pre>
<p>The remainder of the 55000 (&quot;total&quot;, see above) being returned as change.</p>
