"The minimum satoshi value of the output(s) needed (or the string `all` meaning use all unreserved inputs). If a value, it can be a whole number, a whole number ending in *sat*, a whole number ending in *000msat*, or a number with 1 to 8 decimal places ending in *btc*."
]
},
"feerate":{
"type":"feerate",
"description":[
"Used for the transaction as initial feerate."
],
"default":"*normal*"
},
"startweight":{
"type":"u32",
"description":[
"The weight of the transaction before *fundpsbt* has added any inputs."
]
},
"minconf":{
"type":"u32",
"description":[
"The minimum number of confirmations that used outputs should have."
],
"default":"1"
},
"reserve":{
"type":"u32",
"description":[
"If not zero, then *reserveinputs* is called (successfully, with *exclusive* true) on the returned PSBT for this number of blocks."
],
"default":"72 blocks"
},
"locktime":{
"type":"u32",
"description":[
"The locktime of the transaction. if not set, it is set to a recent block height."
]
},
"min_witness_weight":{
"type":"u32",
"description":[
"Minimum weight to use for a UTXO's witness. If the actual witness weight is greater than the provided minimum, the actual witness weight will be used."
]
},
"excess_as_change":{
"type":"boolean",
"description":[
"Flag to add a change output for the excess sats."
]
},
"nonwrapped":{
"added":"v23.02",
"type":"boolean",
"description":[
"To signal to filter out any p2sh-wrapped inputs from funding this PSBT."
]
},
"opening_anchor_channel":{
"added":"v23.08",
"type":"boolean",
"description":[
"To signel that it needs emergency reserve for anchors so that we can lowball our commitment tx fees, and min-emergency-msat for reserving some sats for closing anchor channels."
]
}
}
},
"response":{
"required":[
"psbt",
"feerate_per_kw",
"estimated_final_weight",
"excess_msat"
],
"properties":{
"psbt":{
"type":"string",
"description":[
"Unsigned PSBT which fulfills the parameters given."
]
},
"feerate_per_kw":{
"type":"u32",
"description":[
"The feerate used to create the PSBT, in satoshis-per-kiloweight."
]
},
"estimated_final_weight":{
"type":"u32",
"description":[
"The estimated weight of the transaction once fully signed."
]
},
"excess_msat":{
"type":"msat",
"description":[
"The amount above *satoshi* which is available. This could be zero, or dust; it will be zero if *change_outnum* is also returned."
]
},
"change_outnum":{
"type":"u32",
"description":[
"The 0-based output number where change was placed (only if parameter *excess_as_change* was true and there was sufficient funds)."
]
},
"reservations":{
"type":"array",
"description":[
"If *reserve* was true or a non-zero number, just as per lightning- reserveinputs(7)."
],
"items":{
"type":"object",
"required":[
"txid",
"vout",
"was_reserved",
"reserved",
"reserved_to_block"
],
"additionalProperties":false,
"properties":{
"txid":{
"type":"txid",
"description":[
"The txid of the transaction."
]
},
"vout":{
"type":"u32",
"description":[
"The 0-based output number."
]
},
"was_reserved":{
"type":"boolean",
"enum":[
false
],
"description":[
"Whether this output was previously reserved."
]
},
"reserved":{
"type":"boolean",
"enum":[
true
],
"description":[
"Whether this output is now reserved."
]
},
"reserved_to_block":{
"type":"u32",
"description":[
"The blockheight the reservation will expire."
]
}
}
}
}
},
"post_return_value_notes":[
"If *excess_as_change* is true and the excess is enough to cover an additional output above the `dust_limit`, then an output is added to the PSBT for the excess amount. The *excess_msat* will be zero. A *change_outnum* will be returned with the index of the change output."
]
},
"example_usage":[
"Let's assume the caller is trying to produce a 100,000 satoshi output.",
"",
"First, the caller estimates the weight of the core (typically 42) and known outputs of the transaction (typically (9 + scriptlen) * 4). For a simple P2WPKH it's a 22 byte scriptpubkey, so that's 124 weight.",
"",
"It calls \"*fundpsbt* 100000sat slow 166\", which succeeds, and returns the *psbt* and *feerate_per_kw* it used, the *estimated_final_weight* and any *excess_msat*.",
"",
"If *excess_msat* is greater than the cost of adding a change output, the caller adds a change output randomly to position 0 or 1 in the PSBT. Say *feerate_per_kw* is 253, and the change output is a P2WPKH (weight 124), the cost is around 31 sats. With the dust limit disallowing payments below 546 satoshis, we would only create a change output if *excess_msat* was greater or equal to 31 + 546."
],
"errors":[
"On error the returned object will contain `code` and `message` properties, with `code` being one of the following:",
"",
"- -32602: If the given parameters are wrong.",
"- -1: Catchall nonspecific error.",
"- 301: Insufficient UTXOs to meet *satoshi* value."
