diff --git a/aquamarine-vm/src/args.rs b/aquamarine-vm/src/args.rs
new file mode 100644
index 00000000..ea3f937a
--- /dev/null
+++ b/aquamarine-vm/src/args.rs
@@ -0,0 +1,106 @@
+/*
+ * Copyright 2020 Fluence Labs Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use crate::IValue;
+use crate::args_error::ArgsError;
+use crate::args_error::ArgsError::{MissingField, SerdeJson};
+
+use fluence_faas::SecurityTetraplet;
+
+use serde::Deserialize;
+use serde_json::Value as JValue;
+
+#[derive(Debug)]
+/// Arguments passed by VM to host on call_service
+pub struct CallServiceArgs {
+    pub service_id: String,
+    pub function_name: String,
+    pub function_args: Vec<serde_json::Value>,
+    pub tetraplets: Vec<Vec<SecurityTetraplet>>,
+}
+
+impl CallServiceArgs {
+    /// Construct Args from `Vec<IValue>`
+    pub fn parse(call_args: Vec<IValue>) -> Result<Self, ArgsError> {
+        let mut call_args = call_args.into_iter();
+        let service_id = call_args
+            .next()
+            .and_then(into_string)
+            .ok_or(MissingField("service_id"))?;
+
+        let fname = call_args
+            .next()
+            .and_then(into_string)
+            .ok_or(MissingField("fname"))?;
+
+        let function_args = call_args
+            .next()
+            .as_ref()
+            .and_then(as_str)
+            .ok_or(MissingField("args"))
+            .and_then(|v| {
+                serde_json::from_str(v).map_err(|err| SerdeJson { field: "args", err })
+            })?;
+
+        let tetraplets: Vec<Vec<SecurityTetraplet>> = call_args
+            .next()
+            .as_ref()
+            .and_then(as_str)
+            .ok_or(MissingField("tetraplets"))
+            .and_then(|v| {
+                serde_json::from_str(v).map_err(|err| SerdeJson {
+                    field: "tetraplets",
+                    err,
+                })
+            })?;
+
+        Ok(Self {
+            service_id,
+            function_name: fname,
+            function_args,
+            tetraplets,
+        })
+    }
+
+    /// Retrieves next json value from iterator, parse it to T
+    pub fn next<T: for<'de> Deserialize<'de>>(
+        field: &'static str,
+        args: &mut impl Iterator<Item = JValue>,
+    ) -> Result<T, ArgsError> {
+        let value = args.next().ok_or(MissingField(field))?;
+        let value: T = Self::deserialize(field, value)?;
+
+        Ok(value)
+    }
+
+    /// Retrieves a json value from iterator if it's not empty, and parses it to T
+    pub fn maybe_next<T: for<'de> Deserialize<'de>>(
+        field: &'static str,
+        args: &mut impl Iterator<Item = JValue>,
+    ) -> Result<Option<T>, ArgsError> {
+        let value = ok_get!(args.next());
+        let value: T = Self::deserialize(field, value)?;
+
+        Ok(Some(value))
+    }
+
+    fn deserialize<T: for<'de> Deserialize<'de>>(
+        field: &'static str,
+        v: JValue,
+    ) -> Result<T, ArgsError> {
+        serde_json::from_value(v).map_err(|err| SerdeJson { err, field })
+    }
+}
diff --git a/aquamarine-vm/src/args_error.rs b/aquamarine-vm/src/args_error.rs
new file mode 100644
index 00000000..fdd671a9
--- /dev/null
+++ b/aquamarine-vm/src/args_error.rs
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2020 Fluence Labs Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use serde_json::Value as JValue;
+use std::borrow::Cow;
+use std::error::Error;
+use std::fmt::{Display, Formatter};
+
+#[derive(Debug)]
+pub enum ArgsError {
+    MissingField(&'static str),
+    SerdeJson {
+        field: &'static str,
+        err: serde_json::Error,
+    },
+    InvalidFormat {
+        field: &'static str,
+        err: Cow<'static, str>,
+    },
+}
+
+impl From<ArgsError> for JValue {
+    fn from(err: ArgsError) -> Self {
+        JValue::String(format!("ArgsError: {}", err))
+    }
+}
+
+impl Error for ArgsError {}
+
+impl Display for ArgsError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ArgsError::MissingField(field) => {
+                write!(f, "Field {} is missing from args to call_service", field)
+            }
+            ArgsError::SerdeJson { err, field } => {
+                write!(f, "Error while deserializing field {}: {:?}", field, err)
+            }
+            ArgsError::InvalidFormat { field, err } => {
+                write!(f, "Error while deserializing field {}: {:?}", field, err)
+            }
+        }
+    }
+}
diff --git a/aquamarine-vm/src/lib.rs b/aquamarine-vm/src/lib.rs
index 866b933d..e588ef00 100644
--- a/aquamarine-vm/src/lib.rs
+++ b/aquamarine-vm/src/lib.rs
@@ -27,6 +27,8 @@
 mod aquamarine_stepper_vm;
 mod config;
 mod errors;
+mod args;
+mod args_error;
 
 pub use aquamarine_stepper_vm::AquamarineVM;
 pub use aquamarine_stepper_vm::ParticleParameters;