diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/SolanaClient.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/SolanaClient.kt
index cd9ab5a..9b82564 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/SolanaClient.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/SolanaClient.kt
@@ -1,5 +1,6 @@
 package net.avianlabs.solana
 
+import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.JsonArray
 import net.avianlabs.solana.client.RpcInvocation
@@ -9,10 +10,12 @@ public class SolanaClient(
   private val client: RpcKtorClient,
 ) {
 
+  @OptIn(ExperimentalSerializationApi::class)
   internal val json: Json = Json {
     ignoreUnknownKeys = true
     isLenient = true
     allowSpecialFloatingPointValues = true
+    explicitNulls = false
   }
 
   internal suspend inline fun <reified T> invoke(
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/domain/core/Commitment.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/domain/core/Commitment.kt
new file mode 100644
index 0000000..464d940
--- /dev/null
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/domain/core/Commitment.kt
@@ -0,0 +1,18 @@
+package net.avianlabs.solana.domain.core
+
+
+/**
+ * [Commitment.Finalized] - the node will query the most recent block confirmed by supermajority of the cluster as having reached maximum lockout, meaning the cluster has recognized this block as finalized
+ * [Commitment.Confirmed] - the node will query the most recent block that has been voted on by supermajority of the cluster.
+ * It incorporates votes from gossip and replay.
+ * It does not count votes on descendants of a block, only direct votes on that block.
+ * This confirmation level also upholds "optimistic confirmation" guarantees in release 1.3 and onwards.
+ * [Commitment.Processed] - the node will query its most recent block. Note that the block may still be skipped by the cluster.
+ *
+ * @see <a href="https://docs.solana.com/api/http#configuring-state-commitment">Configuring state commitment</a>
+ */
+public enum class Commitment(public val value: String) {
+  Finalized("finalized"),
+  Confirmed("confirmed"),
+  Processed("processed"),
+}
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getBalance.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getBalance.kt
index e1fbd8a..c3f2a14 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getBalance.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getBalance.kt
@@ -1,18 +1,30 @@
 package net.avianlabs.solana.methods
 
+import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.encodeToJsonElement
 import net.avianlabs.solana.SolanaClient
 import net.avianlabs.solana.client.RpcResponse.RPC
+import net.avianlabs.solana.domain.core.Commitment
 import net.avianlabs.solana.domain.core.PublicKey
 
 public suspend fun SolanaClient.getBalance(
   account: PublicKey,
+  commitment: Commitment? = null,
 ): Long {
-  val result = invoke<RPC<Long>>("getBalance", params(account))
+  val result = invoke<RPC<Long>>("getBalance", params(account, commitment))
   return result!!.value!!
 }
 
 private fun SolanaClient.params(
   account: PublicKey,
-) = JsonArray(listOf(json.encodeToJsonElement(account)))
+  commitment: Commitment?
+) = JsonArray(buildList {
+  add(json.encodeToJsonElement(account))
+  commitment?.let { add(json.encodeToJsonElement(BalanceParams(it.value))) }
+})
+
+@Serializable
+internal data class BalanceParams(
+  val commitment: String? = null,
+)
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getFeeForMessage.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getFeeForMessage.kt
index 3b1b78d..2fcefcd 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getFeeForMessage.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getFeeForMessage.kt
@@ -1,16 +1,30 @@
 package net.avianlabs.solana.methods
 
-import io.ktor.util.*
+import io.ktor.util.encodeBase64
+import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.encodeToJsonElement
 import net.avianlabs.solana.SolanaClient
 import net.avianlabs.solana.client.RpcResponse.RPC
+import net.avianlabs.solana.domain.core.Commitment
 
-public suspend fun SolanaClient.getFeeForMessage(message: ByteArray): Long {
-  val result = invoke<RPC<Long>>("getFeeForMessage", params(message))
+public suspend fun SolanaClient.getFeeForMessage(
+  message: ByteArray,
+  commitment: Commitment? = null
+): Long {
+  val result = invoke<RPC<Long>>("getFeeForMessage", params(message, commitment))
   return result!!.value!!
 }
 
 private fun SolanaClient.params(
   message: ByteArray,
-) = JsonArray(listOf(json.encodeToJsonElement(message.encodeBase64())))
+  commitment: Commitment?,
+) = JsonArray(buildList {
+  add(json.encodeToJsonElement(message.encodeBase64()))
+  commitment?.let { add(json.encodeToJsonElement(FeeForMessageParams(it.value))) }
+})
+
+@Serializable
+internal data class FeeForMessageParams(
+  val commitment: String? = null,
+)
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getMinimumBalanceForRentExemption.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getMinimumBalanceForRentExemption.kt
index 46722f7..18a6513 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getMinimumBalanceForRentExemption.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getMinimumBalanceForRentExemption.kt
@@ -4,10 +4,11 @@ import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.encodeToJsonElement
 import net.avianlabs.solana.SolanaClient
+import net.avianlabs.solana.domain.core.Commitment
 
 public suspend fun SolanaClient.getMinimumBalanceForRentExemption(
   dataLength: Long,
-  commitment: String = "confirmed",
+  commitment: Commitment? = null,
 ): Long {
   val result = invoke<Long>("getMinimumBalanceForRentExemption", params(dataLength, commitment))
   return result!!
@@ -15,15 +16,13 @@ public suspend fun SolanaClient.getMinimumBalanceForRentExemption(
 
 private fun SolanaClient.params(
   dataLength: Long,
-  commitment: String,
-) = JsonArray(
-  listOf(
-    json.encodeToJsonElement(dataLength),
-    json.encodeToJsonElement(GetMinimumBalanceForRentExemptionParams(commitment))
-  )
-)
+  commitment: Commitment?
+) = JsonArray(buildList {
+  add(json.encodeToJsonElement(dataLength))
+  commitment?.let { add(json.encodeToJsonElement(GetMinimumBalanceForRentExemptionParams(it.value))) }
+})
 
 @Serializable
 internal data class GetMinimumBalanceForRentExemptionParams(
-  val commitment: String,
+  val commitment: String? = null,
 )
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getRecentBlockhash.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getRecentBlockhash.kt
index 781b37b..5ee7857 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getRecentBlockhash.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getRecentBlockhash.kt
@@ -5,17 +5,20 @@ import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.encodeToJsonElement
 import net.avianlabs.solana.SolanaClient
 import net.avianlabs.solana.client.RpcResponse
+import net.avianlabs.solana.domain.core.Commitment
 
 public suspend fun SolanaClient.getRecentBlockhash(
-  commitment: String? = null,
+  commitment: Commitment? = null,
 ): RecentBlockHash {
   val rpc = invoke<RpcResponse.RPC<RecentBlockHash>>("getRecentBlockhash", params(commitment))
   return rpc!!.value!!
 }
 
 private fun SolanaClient.params(
-  commitment: String? = null,
-) = JsonArray(listOf(json.encodeToJsonElement(commitment)))
+  commitment: Commitment?,
+) = JsonArray(buildList {
+  commitment?.let { add(json.encodeToJsonElement(it.value)) }
+})
 
 @Serializable
 public data class RecentBlockHash(
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getSignaturesForAddress.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getSignaturesForAddress.kt
index 7e8fb8b..42229c4 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getSignaturesForAddress.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getSignaturesForAddress.kt
@@ -5,27 +5,30 @@ import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.encodeToJsonElement
 import net.avianlabs.solana.SolanaClient
+import net.avianlabs.solana.domain.core.Commitment
 import net.avianlabs.solana.domain.core.PublicKey
 
 public suspend fun SolanaClient.getSignaturesForAddress(
   account: PublicKey,
-  commitment: String?,
+  commitment: Commitment? = null,
 ): List<SignatureInformation> {
-  val rpcParams = SignaturesForAddress(
-    commitment = commitment,
+  val result = invoke<List<SignatureInformation>>(
+    "getSignaturesForAddress",
+    params(account, commitment)
   )
-  val result =
-    invoke<List<SignatureInformation>>("getSignaturesForAddress", params(account, rpcParams))
   return result!!
 }
 
 private fun SolanaClient.params(
   account: PublicKey,
-  rpcParams: SignaturesForAddress,
-) = JsonArray(listOf(json.encodeToJsonElement(account), json.encodeToJsonElement(rpcParams)))
+  commitment: Commitment?
+) = JsonArray(buildList {
+  add(json.encodeToJsonElement(account))
+  commitment?.let { add(json.encodeToJsonElement(SignaturesForAddressParams(commitment = it.value))) }
+})
 
 @Serializable
-internal data class SignaturesForAddress(
+internal data class SignaturesForAddressParams(
   val limit: Long? = null,
   val before: String? = null,
   val until: String? = null,
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getTokenAccountBalance.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getTokenAccountBalance.kt
index 5b3ec4a..2eec5b2 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getTokenAccountBalance.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getTokenAccountBalance.kt
@@ -5,18 +5,29 @@ import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.encodeToJsonElement
 import net.avianlabs.solana.SolanaClient
 import net.avianlabs.solana.client.RpcResponse.RPC
+import net.avianlabs.solana.domain.core.Commitment
 import net.avianlabs.solana.domain.core.PublicKey
 
 public suspend fun SolanaClient.getTokenAccountBalance(
   tokenAccount: PublicKey,
+  commitment: Commitment? = null,
 ): TokenAmountInfo {
-  val result = invoke<RPC<TokenAmountInfo>>("getTokenAccountBalance", params(tokenAccount))
+  val result = invoke<RPC<TokenAmountInfo>>("getTokenAccountBalance", params(tokenAccount, commitment))
   return result!!.value!!
 }
 
 private fun SolanaClient.params(
   account: PublicKey,
-) = JsonArray(listOf(json.encodeToJsonElement(account)))
+  commitment: Commitment?
+) = JsonArray(buildList {
+  add(json.encodeToJsonElement(account))
+  commitment?.let { json.encodeToJsonElement(TokenAccountBalanceParams(it.value)) }
+})
+
+@Serializable
+internal data class TokenAccountBalanceParams(
+  val commitment: String? = null
+)
 
 @Serializable
 public data class TokenAmountInfo(
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getTransaction.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getTransaction.kt
index 1979e20..c571267 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getTransaction.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/getTransaction.kt
@@ -5,21 +5,22 @@ import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.encodeToJsonElement
 import net.avianlabs.solana.SolanaClient
+import net.avianlabs.solana.domain.core.Commitment
 
 public suspend fun SolanaClient.getTransaction(
   signature: String,
-  commitment: String? = null,
+  commitment: Commitment? = null,
 ): TransactionResponse? {
-  val rpcParams = GetTransactionParams(
-    commitment = commitment,
-  )
-  return invoke<TransactionResponse?>("getTransaction", params(signature, rpcParams))
+  return invoke<TransactionResponse?>("getTransaction", params(signature, commitment))
 }
 
 private fun SolanaClient.params(
   signature: String,
-  rpcParams: GetTransactionParams,
-) = JsonArray(listOf(json.encodeToJsonElement(signature), json.encodeToJsonElement(rpcParams)))
+  commitment: Commitment?
+) = JsonArray(buildList {
+  add(json.encodeToJsonElement(signature))
+  commitment?.let { add(json.encodeToJsonElement(GetTransactionParams(it.value))) }
+})
 
 @Serializable
 internal data class GetTransactionParams(
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/isBlockHashValid.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/isBlockHashValid.kt
index cd22196..3a098cc 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/isBlockHashValid.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/isBlockHashValid.kt
@@ -5,10 +5,11 @@ import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.encodeToJsonElement
 import net.avianlabs.solana.SolanaClient
 import net.avianlabs.solana.client.RpcResponse.RPC
+import net.avianlabs.solana.domain.core.Commitment
 
 public suspend fun SolanaClient.isBlockHashValid(
   blockHash: String,
-  commitment: String? = null,
+  commitment: Commitment? = null,
   minContextSlot: Long? = null,
 ): Boolean {
   val result =
@@ -18,14 +19,14 @@ public suspend fun SolanaClient.isBlockHashValid(
 
 private fun SolanaClient.params(
   blockHash: String,
-  commitment: String? = null,
-  minContextSlot: Long? = null,
-) = JsonArray(
-  listOf(
-    json.encodeToJsonElement(blockHash),
-    json.encodeToJsonElement(IsBlockHashValidParams(commitment, minContextSlot))
-  )
-)
+  commitment: Commitment?,
+  minContextSlot: Long?,
+) = JsonArray(buildList {
+  add(json.encodeToJsonElement(blockHash))
+  if (commitment != null || minContextSlot != null) {
+    add(json.encodeToJsonElement(IsBlockHashValidParams(commitment?.value, minContextSlot)))
+  }
+})
 
 @Serializable
 internal data class IsBlockHashValidParams(
diff --git a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/requestAirdrop.kt b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/requestAirdrop.kt
index 4b599a4..6f393c3 100644
--- a/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/requestAirdrop.kt
+++ b/solana-kotlin/src/commonMain/kotlin/net/avianlabs/solana/methods/requestAirdrop.kt
@@ -1,19 +1,32 @@
 package net.avianlabs.solana.methods
 
+import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.encodeToJsonElement
 import net.avianlabs.solana.SolanaClient
+import net.avianlabs.solana.domain.core.Commitment
 import net.avianlabs.solana.domain.core.PublicKey
 
 public suspend fun SolanaClient.requestAirdrop(
   publicKey: PublicKey,
   lamports: Long,
+  commitment: Commitment? = null
 ): String {
-  val result = invoke<String>("requestAirdrop", params(publicKey, lamports))
+  val result = invoke<String>("requestAirdrop", params(publicKey, lamports, commitment))
   return result!!
 }
 
 private fun SolanaClient.params(
   publicKey: PublicKey,
   lamports: Long,
-) = JsonArray(listOf(json.encodeToJsonElement(publicKey), json.encodeToJsonElement(lamports)))
+  commitment: Commitment?
+) = JsonArray(buildList {
+  add(json.encodeToJsonElement(publicKey))
+  add(json.encodeToJsonElement(lamports))
+  commitment?.let { json.encodeToJsonElement(RequestAirdropParams(it.value)) }
+})
+
+@Serializable
+internal data class RequestAirdropParams(
+  val commitment: String? = null,
+)