Last updated

AMMDeposit

[Source]

(Requires the AMM amendment )

Deposit funds into an Automated Market Maker (AMM) instance and receive the AMM's liquidity provider tokens (LP Tokens) in exchange. You can deposit one or both of the assets in the AMM's pool.

If successful, this transaction creates a trust line to the AMM Account (limit 0) to hold the LP Tokens.

Example AMMDeposit JSON

{
    "Account" : "rJVUeRqDFNs2xqA7ncVE6ZoAhPUoaJJSQm",
    "Amount" : {
        "currency" : "TST",
        "issuer" : "rP9jPyP5kyvFRb6ZiRghAGw5u8SGAmU4bd",
        "value" : "2.5"
    },
    "Amount2" : "30000000",
    "Asset" : {
        "currency" : "TST",
        "issuer" : "rP9jPyP5kyvFRb6ZiRghAGw5u8SGAmU4bd"
    },
    "Asset2" : {
        "currency" : "XRP"
    },
    "Fee" : "10",
    "Flags" : 1048576,
    "Sequence" : 7,
    "TransactionType" : "AMMDeposit"
}

AMMDeposit Fields

In addition to the common fields, AMMDeposit transactions use the following fields:

FieldJSON TypeInternal TypeRequired?Description
AssetObjectSTIssueYesThe definition for one of the assets in the AMM's pool. In JSON, this is an object with currency and issuer fields (omit issuer for XRP).
Asset2ObjectSTIssueYesThe definition for the other asset in the AMM's pool. In JSON, this is an object with currency and issuer fields (omit issuer for XRP).
AmountCurrency AmountAmountNoThe amount of one asset to deposit to the AMM. If present, this must match the type of one of the assets (tokens or XRP) in the AMM's pool.
Amount2Currency AmountAmountNoThe amount of another asset to add to the AMM. If present, this must match the type of the other asset in the AMM's pool and cannot be the same asset as Amount.
EPriceCurrency AmountAmountNoThe maximum effective price, in the deposit asset, to pay for each LP Token received.
LPTokenOutCurrency AmountAmountNoHow many of the AMM's LP Tokens to buy.

AMMDeposit Modes

This transaction has five modes, defined by which flag you specify. Each mode expects a specific combination of fields. The modes fall into two categories:

  • Double-asset deposits, in which you provide both assets in the AMM's pool, proportional to the balance of the assets already there. These deposits are not subject to a fee.
  • Single-asset deposits, in which you provide only one of the AMM's two assets. The AMM charges a fee, debited from the LP Tokens paid out, based on how much your deposit shifts the balance of assets in the pool.

The following combinations of fields indicate a double-asset deposit:

Flag NameFlag ValueFields SpecifiedMeaning
tfLPToken0x00010000LPTokenOut onlyDeposit both of this AMM's assets, in amounts calculated so that you receive the specified amount of LP Tokens in return. The amounts deposited maintain the relative proportions of the two assets the AMM already holds.
tfTwoAsset0x00100000Amount and Amount2Deposit both of this AMM's assets, up to the specified amounts. The actual amounts deposited must maintain the same balance of assets as the AMM already holds, so the amount of either one deposited MAY be less than specified. The amount of LP Tokens you get in return is based on the total value deposited.
tfTwoAssetIfEmpty0x00800000Amount and Amount2Deposit both of this AMM's assets, in exactly the specified amounts, to an AMM with an empty asset pool. The amount of LP Tokens you get in return is based on the total value deposited.

The following combinations of fields indicate a single asset deposit:

Flag NameFlag ValueFields SpecifiedMeaning
tfSingleAsset0x00080000Amount onlyDeposit exactly the specified amount of one asset, and receive an amount of LP Tokens based on the resulting share of the pool (minus fees).
tfOneAssetLPToken0x00200000Amount and LPTokenOutDeposit up to the specified amount of one asset, so that you receive exactly the specified amount of LP Tokens in return (after fees).
tfLimitLPToken0x00400000Amount and EPriceDeposit up to the specified amount of one asset, but pay no more than the specified effective price per LP Token (after fees).

Any other combination of these fields and flags is invalid.

Single Asset Deposit Fee

The fee for a single asset deposit is calculated to be the same as if you had used the AMM to trade part of the deposit amount for the other asset, then done a double-asset deposit. The AMM's trading fee applies to the amount you would need to trade for, but not to the rest of the deposit. For example, if the AMM's asset pool is split perfectly evenly between USD and EUR, and you try to deposit 100 USD, the amount of LP Tokens you receive is slightly less than if you had deposited 50 EUR + 50 USD, because you pay the trading fee to convert some of your USD to an equal amount of EUR.

The formula for how many LP Tokens you receive for a double-asset deposit is:

1 +B - (F × (1 - W) × B)P][)(W- 1L = T ×

Where:

  • L is the amount of LP Tokens returned
  • T is the total outstanding LP Tokens before the deposit
  • B is the amount of the asset being deposited
  • F is the trading fee, as a decimal
  • W is the weight of the deposit asset in the pool. This is defined as 0.5 for all AMM pools (meaning a 50/50 split), so exponentiation by W is equivalent to taking the square root.
  • P is the total amount of the deposit asset in the pool before the deposit

Empty AMM Special Case

In some cases, an AMM can exist with no assets in its pool. You cannot perform normal deposits into an AMM in such a state because the ratio between the assets is undefined (0/0). Instead, you can use a special "Empty AMM" deposit case with the flag tfTwoAssetIfEmpty and exact amounts of both assets. This directly sets the ratio between the assets in the same way an AMMCreate transaction does when an AMM is initially created. Like a double-asset deposit, this is not subject to a fee.

You can only do a special "Empty AMM" deposit if the AMM is empty.

AMMDeposit Flags

Transactions of the AMMDeposit type support additional values in the Flags field, as follows:

Flag NameHex ValueDecimal ValueDescription
tfLPToken0x0001000065536Perform a double-asset deposit and receive the specified amount of LP Tokens.
tfSingleAsset0x00080000524288Perform a single-asset deposit with a specified amount of the asset to deposit.
tfTwoAsset0x001000001048576Perform a double-asset deposit with specified amounts of both assets.
tfOneAssetLPToken0x002000002097152Perform a single-asset deposit and receive the specified amount of LP Tokens.
tfLimitLPToken0x004000004194304Perform a single-asset deposit with a specified effective price.
tfTwoAssetIfEmpty0x008000008388608Perform a special double-asset deposit to an AMM with an empty pool.

You must specify exactly one of these flags, plus any global flags.

Error Cases

Besides errors that can occur for all transactions, AMMDeposit transactions can result in the following transaction result codes:

Error CodeDescription
tecAMM_EMPTYThe AMM currently holds no assets, so you cannot do a normal deposit. You must use the Empty AMM Special Case deposit instead.
tecAMM_NOT_EMPTYThe transaction specified tfTwoAssetIfEmpty, but the AMM was not empty.
tecAMM_FAILEDThe conditions on the deposit could not be satisfied. For example, the requested effective price in the EPrice field is too low.
tecFROZENThe transaction tried to deposit a frozen token.
tecINSUF_RESERVE_LINEThe sender of this transaction does meet the increased reserve requirement of processing this transaction, probably because they need a new trust line to hold the LP Tokens, and they don't have enough XRP to meet the additional owner reserve for a new trust line.
tecUNFUNDED_AMMThe sender does not have a high enough balance to make the specified deposit.
temBAD_AMM_TOKENSThe transaction specified the LP Tokens incorrectly. For example, the issuer is not the AMM's associated AccountRoot address or the currency is not the currency code for this AMM's LP Tokens, or the transaction specified this AMM's LP Tokens in one of the asset fields.
temBAD_AMOUNTAn amount specified in the transaction is invalid. For example, a deposit amount is negative.
temBAD_FEEA fee value specified in the transaction is invalid. For example, the trading fee is outside the allowable range.
temMALFORMEDThe transaction specified an invalid combination of fields. See AMMDeposit Modes.
terNO_ACCOUNTAn account specified in the request does not exist.
terNO_AMMThe Automated Market Maker instance for the asset pair in this transaction does not exist.