The server_definitions command returns an SDK-compatible definitions.json, generated from the xrpld instance currently running. You can use this to query a node in a network, quickly receiving the definitions necessary to serialize/deserialize its binary data.
The response also includes the TRANSACTION_FORMATS, LEDGER_ENTRY_FORMATS, TRANSACTION_FLAGS, LEDGER_ENTRY_FLAGS, and ACCOUNT_SET_FLAGS sections, which describe the fields and flags of each transaction and ledger entry type. 
You can also generate the same definitions without a running server using the --definitions command-line flag.
An example of the request format:
{
"id": 2,
"command": "server_definitions"
}The request includes the following parameters:
| Field | Type | Required? | Description |
|---|---|---|---|
hash | String | No | If included and the hash matches the server's hash, the full set of definitions will not be returned. |
An example of a successful response:
{
"id": 1,
"result": {
"FIELDS": [
[
"Generic",
{
"isSerialized": false,
"isSigningField": false,
"isVLEncoded": false,
"nth": 0,
"type": "Unknown"
}
],
[
"Invalid",
{
"isSerialized": false,
"isSigningField": false,
"isVLEncoded": false,
"nth": -1,
"type": "Unknown"
}
],
[
"ObjectEndMarker",
{
"isSerialized": true,
"isSigningField": true,
"isVLEncoded": false,
"nth": 1,
"type": "STObject"
}
],
[
"ArrayEndMarker",
{
"isSerialized": true,
"isSigningField": true,
"isVLEncoded": false,
"nth": 1,
"type": "STArray"
}
]
...
],
"TRANSACTION_FORMATS": {
"common": [
{
"name": "TransactionType",
"optionality": 0
},
{
"name": "Flags",
"optionality": 1
},
{
"name": "SourceTag",
"optionality": 1
}
...
],
"AccountSet": [
{
"name": "EmailHash",
"optionality": 1
},
...
{
"name": "SetFlag",
"optionality": 1
}
...
]
...
},
"LEDGER_ENTRY_FORMATS": {
"common": [
{
"name": "LedgerIndex",
"optionality": 1
},
{
"name": "LedgerEntryType",
"optionality": 0
},
{
"name": "Flags",
"optionality": 0
}
],
"DID": [
{
"name": "Account",
"optionality": 0
},
{
"name": "DIDDocument",
"optionality": 1
}
...
]
...
},
"TRANSACTION_FLAGS": {
"universal": {
"tfFullyCanonicalSig": 2147483648,
"tfInnerBatchTxn": 1073741824
},
"AccountSet": {
"tfRequireDestTag": 65536,
"tfOptionalDestTag": 131072
...
}
...
},
"LEDGER_ENTRY_FLAGS": {
"AccountRoot": {
"lsfDisallowXRP": 524288
...
}
...
},
"ACCOUNT_SET_FLAGS": {
"asfRequireDest": 1,
"asfRequireAuth": 2,
"asfDisallowXRP": 3
...
}
}
}To see a full definitions.json file and descriptions of the top-level fields—including the TRANSACTION_FORMATS, LEDGER_ENTRY_FORMATS, TRANSACTION_FLAGS, LEDGER_ENTRY_FLAGS, and ACCOUNT_SET_FLAGS sections—see: Definitions File.
Any of the universal error types.