diff --git a/bindings/c-ffi/example.c b/bindings/c-ffi/example.c
index 43fa14f..4f7abac 100644
--- a/bindings/c-ffi/example.c
+++ b/bindings/c-ffi/example.c
@@ -20,9 +20,9 @@ int main() {
     char wallet_data[300];
     sprintf(wallet_data,
             "{ \"data_dir\": \"./data\", \"bitcoin_network\": \"Regtest\", "
-            "\"database_type\": \"Sqlite\", \"max_allocations_per_utxo\": 1, "
-            "\"pubkey\": \"%s\", \"mnemonic\": \"%s\", \"vanilla_keychain\": "
-            "null }",
+            "\"database_type\": \"Sqlite\", \"max_allocations_per_utxo\": "
+            "\"1\", \"pubkey\": \"%s\", \"mnemonic\": \"%s\", "
+            "\"vanilla_keychain\": null }",
             account_xpub, mnemonic);
 
     printf("Creating wallet...\n");
@@ -82,7 +82,7 @@ int main() {
     printf("BTC balance after sync: %s\n", btc_balance_2);
 
     CResultString created_res =
-        rgblib_create_utxos(wlt, online, false, "25", NULL, 1.5, false);
+        rgblib_create_utxos(wlt, online, false, "25", NULL, "1.5", false);
     if (created_res.result == Err) {
         printf("ERR: %s\n", created_res.inner);
         return EXIT_FAILURE;
@@ -90,8 +90,8 @@ int main() {
     const char *created = created_res.inner;
     printf("Created %s UTXOs\n", created);
 
-    CResultString asset_nia_res =
-        rgblib_issue_asset_nia(wlt, online, "USDT", "Tether", 2, "[777, 66]");
+    CResultString asset_nia_res = rgblib_issue_asset_nia(
+        wlt, online, "USDT", "Tether", "2", "[\"777\", \"66\"]");
     if (asset_nia_res.result == Ok) {
         printf("Issued a NIA asset: %s\n", asset_nia_res.inner);
     } else {
@@ -99,8 +99,8 @@ int main() {
         return EXIT_FAILURE;
     }
 
-    CResultString asset_cfa_res =
-        rgblib_issue_asset_cfa(wlt, online, "Cfa", "desc", 2, "[777]", NULL);
+    CResultString asset_cfa_res = rgblib_issue_asset_cfa(
+        wlt, online, "Cfa", "desc", "2", "[\"777\"]", NULL);
     if (asset_cfa_res.result == Ok) {
         printf("Issued a CFA asset: %s\n", asset_cfa_res.inner);
     } else {
@@ -109,7 +109,7 @@ int main() {
     }
 
     CResultString asset_uda_res = rgblib_issue_asset_uda(
-        wlt, online, "TKN", "Token", NULL, 2, "README.md", "[]");
+        wlt, online, "TKN", "Token", NULL, "2", "README.md", "[]");
     if (asset_uda_res.result == Ok) {
         printf("Issued a UDA asset: %s\n", asset_uda_res.inner);
     } else {
@@ -139,7 +139,7 @@ int main() {
 
     const char *transport_endpoints = "[\"rpc://127.0.0.1:3000/json-rpc\"]";
     CResultString receive_data_res =
-        rgblib_blind_receive(wlt, NULL, NULL, NULL, transport_endpoints, 1);
+        rgblib_blind_receive(wlt, NULL, NULL, NULL, transport_endpoints, "1");
     if (receive_data_res.result == Ok) {
         printf("Receive data: %s\n", receive_data_res.inner);
     } else {
@@ -155,7 +155,7 @@ int main() {
         return EXIT_FAILURE;
     }
 
-    CResultString fee_res = rgblib_get_fee_estimation(wlt, online, 7);
+    CResultString fee_res = rgblib_get_fee_estimation(wlt, online, "7");
     printf("Fee estimation: %s\n", fee_res.inner);
 
     return EXIT_SUCCESS;
diff --git a/bindings/c-ffi/src/lib.rs b/bindings/c-ffi/src/lib.rs
index 7ee0416..9ddd8db 100644
--- a/bindings/c-ffi/src/lib.rs
+++ b/bindings/c-ffi/src/lib.rs
@@ -5,7 +5,7 @@ use crate::utils::*;
 use std::{
     any::TypeId,
     collections::{hash_map::DefaultHasher, HashMap},
-    ffi::{c_char, c_float, c_uchar, c_ushort, c_void, CStr, CString},
+    ffi::{c_char, c_void, CStr, CString},
     hash::{Hash, Hasher},
     ptr::null_mut,
     str::FromStr,
@@ -61,7 +61,7 @@ pub extern "C" fn rgblib_blind_receive(
     amount_opt: *const c_char,
     duration_seconds_opt: *const c_char,
     transport_endpoints: *const c_char,
-    min_confirmations: c_uchar,
+    min_confirmations: *const c_char,
 ) -> CResultString {
     blind_receive(
         wallet,
@@ -81,7 +81,7 @@ pub extern "C" fn rgblib_create_utxos(
     up_to: bool,
     num_opt: *const c_char,
     size_opt: *const c_char,
-    fee_rate: c_float,
+    fee_rate: *const c_char,
     skip_sync: bool,
 ) -> CResultString {
     create_utxos(
@@ -121,7 +121,7 @@ pub extern "C" fn rgblib_get_btc_balance(
 pub extern "C" fn rgblib_get_fee_estimation(
     wallet: &COpaqueStruct,
     online: &COpaqueStruct,
-    blocks: c_ushort,
+    blocks: *const c_char,
 ) -> CResultString {
     get_fee_estimation(wallet, online, blocks).into()
 }
@@ -141,7 +141,7 @@ pub extern "C" fn rgblib_issue_asset_cfa(
     online: &COpaqueStruct,
     name: *const c_char,
     details_opt: *const c_char,
-    precision: c_uchar,
+    precision: *const c_char,
     amounts: *const c_char,
     file_path_opt: *const c_char,
 ) -> CResultString {
@@ -163,7 +163,7 @@ pub extern "C" fn rgblib_issue_asset_nia(
     online: &COpaqueStruct,
     ticker: *const c_char,
     name: *const c_char,
-    precision: c_uchar,
+    precision: *const c_char,
     amounts: *const c_char,
 ) -> CResultString {
     issue_asset_nia(wallet, online, ticker, name, precision, amounts).into()
@@ -176,7 +176,7 @@ pub extern "C" fn rgblib_issue_asset_uda(
     ticker: *const c_char,
     name: *const c_char,
     details_opt: *const c_char,
-    precision: c_uchar,
+    precision: *const c_char,
     media_file_path_opt: *const c_char,
     attachments_file_paths: *const c_char,
 ) -> CResultString {
@@ -258,8 +258,8 @@ pub extern "C" fn rgblib_send(
     online: &COpaqueStruct,
     recipient_map: *const c_char,
     donation: bool,
-    fee_rate: c_float,
-    min_confirmations: c_uchar,
+    fee_rate: *const c_char,
+    min_confirmations: *const c_char,
     skip_sync: bool,
 ) -> CResultString {
     send(
@@ -279,8 +279,8 @@ pub extern "C" fn rgblib_send_btc(
     wallet: &COpaqueStruct,
     online: &COpaqueStruct,
     address: *const c_char,
-    amount: u64,
-    fee_rate: c_float,
+    amount: *const c_char,
+    fee_rate: *const c_char,
     skip_sync: bool,
 ) -> CResultString {
     send_btc(wallet, online, address, amount, fee_rate, skip_sync).into()
@@ -298,7 +298,7 @@ pub extern "C" fn rgblib_witness_receive(
     amount_opt: *const c_char,
     duration_seconds_opt: *const c_char,
     transport_endpoints: *const c_char,
-    min_confirmations: c_uchar,
+    min_confirmations: *const c_char,
 ) -> CResultString {
     witness_receive(
         wallet,
diff --git a/bindings/c-ffi/src/utils.rs b/bindings/c-ffi/src/utils.rs
index b46cc92..b61a816 100644
--- a/bindings/c-ffi/src/utils.rs
+++ b/bindings/c-ffi/src/utils.rs
@@ -5,6 +5,9 @@ pub(crate) enum Error {
     #[error("Error converting JSON: {0}")]
     JSONConversion(#[from] serde_json::Error),
 
+    #[error("Error converting string into number")]
+    StringToNumberConversion,
+
     #[error("Error from rgb-lib: {0}")]
     RgbLib(#[from] RgbLibError),
 
@@ -103,6 +106,15 @@ where
     }
 }
 
+fn convert_strings_array<T: FromStr>(ptr: *const c_char) -> Result<Vec<T>, Error> {
+    let str_array: Vec<String> = serde_json::from_str(&ptr_to_string(ptr))?;
+    str_array
+        .iter()
+        .map(|a| a.parse())
+        .collect::<Result<Vec<T>, _>>()
+        .map_err(|_| Error::StringToNumberConversion)
+}
+
 fn convert_optional_number<T: serde::de::DeserializeOwned>(
     ptr: *const c_char,
 ) -> Result<Option<T>, Error> {
@@ -132,6 +144,12 @@ fn convert_optional_string(ptr: *const c_char) -> Option<String> {
     }
 }
 
+fn ptr_to_num<T: FromStr>(ptr: *const c_char) -> Result<T, Error> {
+    ptr_to_string(ptr)
+        .parse()
+        .map_err(|_| Error::StringToNumberConversion)
+}
+
 fn ptr_to_string(ptr: *const c_char) -> String {
     unsafe { CStr::from_ptr(ptr).to_string_lossy().into_owned() }
 }
@@ -154,14 +172,15 @@ pub(crate) fn blind_receive(
     amount_opt: *const c_char,
     duration_seconds_opt: *const c_char,
     transport_endpoints: *const c_char,
-    min_confirmations: c_uchar,
+    min_confirmations: *const c_char,
 ) -> Result<String, Error> {
     let wallet = Wallet::from_opaque(wallet)?;
     let transport_endpoints: Vec<String> =
         serde_json::from_str(&ptr_to_string(transport_endpoints))?;
     let asset_id = convert_optional_string(asset_id_opt);
-    let amount: Option<u64> = convert_optional_number(amount_opt)?;
-    let duration_seconds: Option<u32> = convert_optional_number(duration_seconds_opt)?;
+    let amount = convert_optional_number(amount_opt)?;
+    let duration_seconds = convert_optional_number(duration_seconds_opt)?;
+    let min_confirmations = ptr_to_num(min_confirmations)?;
     let res = wallet.blind_receive(
         asset_id,
         amount,
@@ -178,13 +197,14 @@ pub(crate) fn create_utxos(
     up_to: bool,
     num_opt: *const c_char,
     size_opt: *const c_char,
-    fee_rate: c_float,
+    fee_rate: *const c_char,
     skip_sync: bool,
 ) -> Result<String, Error> {
     let wallet = Wallet::from_opaque(wallet)?;
     let online = Online::from_opaque(online)?;
-    let num: Option<u8> = convert_optional_number(num_opt)?;
-    let size: Option<u32> = convert_optional_number(size_opt)?;
+    let num = convert_optional_number(num_opt)?;
+    let size = convert_optional_number(size_opt)?;
+    let fee_rate = ptr_to_num(fee_rate)?;
     let res = wallet.create_utxos((*online).clone(), up_to, num, size, fee_rate, skip_sync)?;
     Ok(serde_json::to_string(&res)?)
 }
@@ -224,10 +244,11 @@ pub(crate) fn get_btc_balance(
 pub(crate) fn get_fee_estimation(
     wallet: &COpaqueStruct,
     online: &COpaqueStruct,
-    blocks: c_ushort,
+    blocks: *const c_char,
 ) -> Result<String, Error> {
     let wallet = Wallet::from_opaque(wallet)?;
     let online = Online::from_opaque(online)?;
+    let blocks = ptr_to_num(blocks)?;
     let res = wallet.get_fee_estimation((*online).clone(), blocks)?;
     Ok(serde_json::to_string(&res)?)
 }
@@ -246,13 +267,14 @@ pub(crate) fn issue_asset_cfa(
     online: &COpaqueStruct,
     name: *const c_char,
     details_opt: *const c_char,
-    precision: c_uchar,
+    precision: *const c_char,
     amounts: *const c_char,
     file_path_opt: *const c_char,
 ) -> Result<String, Error> {
     let wallet = Wallet::from_opaque(wallet)?;
     let online = Online::from_opaque(online)?;
-    let amounts: Vec<u64> = serde_json::from_str(&ptr_to_string(amounts))?;
+    let precision = ptr_to_num(precision)?;
+    let amounts = convert_strings_array(amounts)?;
     let details = convert_optional_string(details_opt);
     let file_path = convert_optional_string(file_path_opt);
     let res = wallet.issue_asset_cfa(
@@ -271,12 +293,13 @@ pub(crate) fn issue_asset_nia(
     online: &COpaqueStruct,
     ticker: *const c_char,
     name: *const c_char,
-    precision: c_uchar,
+    precision: *const c_char,
     amounts: *const c_char,
 ) -> Result<String, Error> {
     let wallet = Wallet::from_opaque(wallet)?;
     let online = Online::from_opaque(online)?;
-    let amounts: Vec<u64> = serde_json::from_str(&ptr_to_string(amounts))?;
+    let precision = ptr_to_num(precision)?;
+    let amounts = convert_strings_array(amounts)?;
     let res = wallet.issue_asset_nia(
         (*online).clone(),
         ptr_to_string(ticker),
@@ -294,13 +317,14 @@ pub(crate) fn issue_asset_uda(
     ticker: *const c_char,
     name: *const c_char,
     details_opt: *const c_char,
-    precision: c_uchar,
+    precision: *const c_char,
     media_file_path_opt: *const c_char,
     attachments_file_paths: *const c_char,
 ) -> Result<String, Error> {
     let wallet = Wallet::from_opaque(wallet)?;
     let online = Online::from_opaque(online)?;
     let details = convert_optional_string(details_opt);
+    let precision = ptr_to_num(precision)?;
     let media_file_path = convert_optional_string(media_file_path_opt);
     let attachments_file_paths: Vec<String> =
         serde_json::from_str(&ptr_to_string(attachments_file_paths))?;
@@ -395,14 +419,16 @@ pub(crate) fn send(
     online: &COpaqueStruct,
     recipient_map: *const c_char,
     donation: bool,
-    fee_rate: c_float,
-    min_confirmations: c_uchar,
+    fee_rate: *const c_char,
+    min_confirmations: *const c_char,
     skip_sync: bool,
 ) -> Result<String, Error> {
     let wallet = Wallet::from_opaque(wallet)?;
     let online = Online::from_opaque(online)?;
     let recipient_map: HashMap<String, Vec<Recipient>> =
         serde_json::from_str(&ptr_to_string(recipient_map))?;
+    let fee_rate = ptr_to_num(fee_rate)?;
+    let min_confirmations = ptr_to_num(min_confirmations)?;
     let res = wallet.send(
         (*online).clone(),
         recipient_map,
@@ -418,13 +444,15 @@ pub(crate) fn send_btc(
     wallet: &COpaqueStruct,
     online: &COpaqueStruct,
     address: *const c_char,
-    amount: u64,
-    fee_rate: c_float,
+    amount: *const c_char,
+    fee_rate: *const c_char,
     skip_sync: bool,
 ) -> Result<String, Error> {
     let wallet = Wallet::from_opaque(wallet)?;
     let online = Online::from_opaque(online)?;
     let address = ptr_to_string(address);
+    let amount = ptr_to_num(amount)?;
+    let fee_rate = ptr_to_num(fee_rate)?;
     let res = wallet.send_btc((*online).clone(), address, amount, fee_rate, skip_sync)?;
     Ok(res)
 }
@@ -442,14 +470,15 @@ pub(crate) fn witness_receive(
     amount_opt: *const c_char,
     duration_seconds_opt: *const c_char,
     transport_endpoints: *const c_char,
-    min_confirmations: c_uchar,
+    min_confirmations: *const c_char,
 ) -> Result<String, Error> {
     let wallet = Wallet::from_opaque(wallet)?;
     let transport_endpoints: Vec<String> =
         serde_json::from_str(&ptr_to_string(transport_endpoints))?;
     let asset_id = convert_optional_string(asset_id_opt);
-    let amount: Option<u64> = convert_optional_number(amount_opt)?;
-    let duration_seconds: Option<u32> = convert_optional_number(duration_seconds_opt)?;
+    let amount = convert_optional_number(amount_opt)?;
+    let duration_seconds = convert_optional_number(duration_seconds_opt)?;
+    let min_confirmations = ptr_to_num(min_confirmations)?;
     let res = wallet.witness_receive(
         asset_id,
         amount,
diff --git a/src/lib.rs b/src/lib.rs
index 0146a76..2a32dc7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -223,7 +223,8 @@ use sea_orm::{
     EntityTrait, EnumIter, IntoActiveValue, QueryFilter, QueryOrder, TryIntoModel,
 };
 use seals::SecretSeal;
-use serde::{Deserialize, Serialize};
+use serde::de::{self, Unexpected, Visitor};
+use serde::{Deserialize, Deserializer, Serialize};
 use slog::{debug, error, info, o, warn, Drain, Logger};
 use slog_async::AsyncGuard;
 use slog_term::{FullFormat, PlainDecorator};
@@ -286,7 +287,8 @@ use crate::{
     error::InternalError,
     utils::{
         adjust_canonicalization, beneficiary_from_script_buf, calculate_descriptor_from_xprv,
-        calculate_descriptor_from_xpub, derive_account_xprv_from_mnemonic, get_xpub_from_xprv,
+        calculate_descriptor_from_xpub, derive_account_xprv_from_mnemonic,
+        from_str_or_number_mandatory, from_str_or_number_optional, get_xpub_from_xprv,
         load_rgb_runtime, now, setup_logger, RgbInExt, RgbOutExt, RgbPsbtExt, RgbRuntime, LOG_FILE,
     },
     wallet::{Balance, Outpoint, NUM_KNOWN_SCHEMAS, SCHEMA_ID_CFA, SCHEMA_ID_NIA, SCHEMA_ID_UDA},
diff --git a/src/utils.rs b/src/utils.rs
index 853ea0f..a69e67c 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -140,6 +140,91 @@ pub(crate) fn adjust_canonicalization<P: AsRef<Path>>(p: P) -> String {
     }
 }
 
+fn deserialize_str_or_number<'de, D, T>(deserializer: D) -> Result<Option<T>, D::Error>
+where
+    D: Deserializer<'de>,
+    T: FromStr + Copy,
+    T::Err: fmt::Display,
+{
+    struct StringOrNumberVisitor<T>(std::marker::PhantomData<T>);
+
+    impl<'de, T> Visitor<'de> for StringOrNumberVisitor<T>
+    where
+        T: FromStr + Copy,
+        T::Err: fmt::Display,
+    {
+        type Value = Option<T>;
+
+        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+            formatter.write_str("a string, a number, or null")
+        }
+
+        fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            T::from_str(&value.to_string())
+                .map(Some)
+                .map_err(de::Error::custom)
+        }
+
+        fn visit_f64<E>(self, value: f64) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            T::from_str(&value.to_string())
+                .map(Some)
+                .map_err(de::Error::custom)
+        }
+
+        fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            value.parse::<T>().map(Some).map_err(|e| {
+                de::Error::invalid_value(Unexpected::Str(value), &e.to_string().as_str())
+            })
+        }
+
+        fn visit_none<E>(self) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            Ok(None)
+        }
+
+        fn visit_unit<E>(self) -> Result<Self::Value, E>
+        where
+            E: de::Error,
+        {
+            Ok(None)
+        }
+    }
+
+    deserializer.deserialize_any(StringOrNumberVisitor(std::marker::PhantomData))
+}
+
+pub(crate) fn from_str_or_number_mandatory<'de, D, T>(deserializer: D) -> Result<T, D::Error>
+where
+    D: Deserializer<'de>,
+    T: FromStr + Copy,
+    T::Err: fmt::Display,
+{
+    match deserialize_str_or_number(deserializer)? {
+        Some(val) => Ok(val),
+        None => Err(de::Error::custom("expected a number but got null")),
+    }
+}
+
+pub(crate) fn from_str_or_number_optional<'de, D, T>(deserializer: D) -> Result<Option<T>, D::Error>
+where
+    D: Deserializer<'de>,
+    T: FromStr + Copy,
+    T::Err: fmt::Display,
+{
+    deserialize_str_or_number(deserializer)
+}
+
 #[cfg_attr(not(any(feature = "electrum", feature = "esplora")), allow(dead_code))]
 fn get_genesis_hash(bitcoin_network: &BitcoinNetwork) -> &str {
     match bitcoin_network {
diff --git a/src/wallet/offline.rs b/src/wallet/offline.rs
index 03e73b9..a7695c5 100644
--- a/src/wallet/offline.rs
+++ b/src/wallet/offline.rs
@@ -850,6 +850,7 @@ pub struct Recipient {
     /// Witness data (to be provided only with a witness recipient)
     pub witness_data: Option<WitnessData>,
     /// RGB amount
+    #[serde(deserialize_with = "from_str_or_number_mandatory")]
     pub amount: u64,
     /// Transport endpoints
     pub transport_endpoints: Vec<String>,
@@ -860,8 +861,10 @@ pub struct Recipient {
 #[cfg_attr(feature = "camel_case", serde(rename_all = "camelCase"))]
 pub struct WitnessData {
     /// The Bitcoin amount (in sats) to send to the recipient
+    #[serde(deserialize_with = "from_str_or_number_mandatory")]
     pub amount_sat: u64,
     /// An optional blinding
+    #[serde(deserialize_with = "from_str_or_number_optional")]
     pub blinding: Option<u64>,
 }
 
@@ -1101,12 +1104,14 @@ pub struct WalletData {
     /// Database type for the wallet
     pub database_type: DatabaseType,
     /// The max number of RGB allocations allowed per UTXO
+    #[serde(deserialize_with = "from_str_or_number_mandatory")]
     pub max_allocations_per_utxo: u32,
     /// Wallet account-level xPub
     pub pubkey: String,
     /// Wallet mnemonic phrase
     pub mnemonic: Option<String>,
     /// Keychain index for the vanilla wallet (default: 1)
+    #[serde(deserialize_with = "from_str_or_number_optional")]
     pub vanilla_keychain: Option<u8>,
 }