diff --git a/crates/cli/src/lib.rs b/crates/cli/src/lib.rs
index e9d8c9af..2ca894cf 100644
--- a/crates/cli/src/lib.rs
+++ b/crates/cli/src/lib.rs
@@ -9,9 +9,9 @@ pub struct Args {
 }
 
 pub fn get_config(args: Args) -> eyre::Result<Config> {
-    Ok(if let Some(path) = args.config.as_ref() {
-        Config::from_file(path)?
+    if let Some(path) = args.config.as_ref() {
+        Config::from_file(path)
     } else {
         Config::from_env()
-    })
+    }
 }
diff --git a/crates/core/src/config.rs b/crates/core/src/config.rs
index 956d66b6..79442e0e 100644
--- a/crates/core/src/config.rs
+++ b/crates/core/src/config.rs
@@ -4,7 +4,7 @@ use std::path::PathBuf;
 use std::str::FromStr;
 
 use ethers::types::Address;
-use eyre::{eyre, Result};
+use eyre::{eyre, Context, Result};
 use helios::client::{Client, ClientBuilder};
 use helios::config::checkpoints;
 use helios::config::networks::Network;
@@ -84,25 +84,37 @@ impl Default for Config {
 }
 
 impl Config {
-    pub fn from_env() -> Self {
-        Self {
-            network: Network::from_str(
-                &std::env::var("NETWORK").unwrap_or_default(),
-            )
-            .unwrap_or(Network::MAINNET),
-            eth_execution_rpc: std::env::var("ETH_EXECUTION_RPC")
-                .unwrap_or_default(),
-            starknet_rpc: std::env::var("STARKNET_RPC").unwrap_or_default(),
-            data_dir: PathBuf::from(
-                std::env::var("DATA_DIR").unwrap_or_default(),
-            ),
-            poll_secs: u64::from_str(
-                &std::env::var("POLL_SECS").unwrap_or_default(),
-            )
-            .unwrap_or(DEFAULT_POLL_SECS),
-            rpc_addr: rpc_addr(),
-            fee_token_addr: fee_token_addr(),
-        }
+    pub fn from_env() -> Result<Self> {
+        Self::from_vars(|key| std::env::var(key).ok())
+    }
+
+    fn from_vars<F>(get: F) -> Result<Self>
+    where
+        F: Fn(&'static str) -> Option<String> + 'static,
+    {
+        let require = |var_key: &'static str| {
+            get(var_key).ok_or_else(|| eyre!("The \"{}\" env var must be set or a configuration file must be specified", var_key))
+        };
+
+        Ok(Self {
+            network: Network::from_str(&get("NETWORK").unwrap_or_default())
+                .unwrap_or(Network::MAINNET),
+            eth_execution_rpc: require("ETH_EXECUTION_RPC")?,
+            starknet_rpc: require("STARKNET_RPC")?,
+            data_dir: PathBuf::from(get("DATA_DIR").unwrap_or_default()),
+            poll_secs: u64::from_str(&get("POLL_SECS").unwrap_or_default())
+                .unwrap_or(DEFAULT_POLL_SECS),
+            rpc_addr: match get("RPC_ADDR") {
+                Some(addr) => SocketAddr::from_str(&addr)
+                    .context("Invalid value for `RPC_ADDR`")?,
+                None => rpc_addr(),
+            },
+            fee_token_addr: match get("FEE_TOKEN_ADDR") {
+                Some(addr) => FieldElement::from_hex_be(&addr)
+                    .context("Invalid value for `FEE_TOKEN_ADDR`")?,
+                None => fee_token_addr(),
+            },
+        })
     }
 
     pub fn from_file(path: &str) -> Result<Self> {
@@ -201,3 +213,79 @@ impl Config {
             .expect("incorrect helios client config")
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::collections::HashMap;
+
+    use super::*;
+
+    fn case(vars: &[(&'static str, &'static str)]) -> Result<Config> {
+        let vars: HashMap<&str, &str> = HashMap::from_iter(vars.to_vec());
+        Config::from_vars(move |s| vars.get(s).map(|s| s.to_string()))
+    }
+
+    static MIN_CONFIG_VARS: &[(&'static str, &'static str)] =
+        &[("ETH_EXECUTION_RPC", "url"), ("STARKNET_RPC", "url")];
+
+    #[test]
+    fn test_min_config_requirements() {
+        assert!(case(&[("ETH_EXECUTION_RPC", "url"),]).is_err());
+        assert!(case(&[("STARKNET_RPC", "url"),]).is_err());
+
+        assert!(case(&MIN_CONFIG_VARS).is_ok());
+    }
+
+    #[test]
+    fn test_unspecified_network_is_mainnet() {
+        let config = case(&MIN_CONFIG_VARS).unwrap();
+        assert_eq!(config.network, Network::MAINNET);
+    }
+
+    #[test]
+    fn test_rpc_address_is_validated() {
+        let result = case(&[
+            ("ETH_EXECUTION_RPC", "url"),
+            ("STARKNET_RPC", "url"),
+            ("RPC_ADDR", "invalid_value"),
+        ]);
+        assert!(result.is_err());
+
+        let result = case(&[
+            ("ETH_EXECUTION_RPC", "url"),
+            ("STARKNET_RPC", "url"),
+            ("RPC_ADDR", "127.0.0.1:3333"),
+        ]);
+        assert!(result.is_ok());
+        assert_eq!(
+            SocketAddr::from_str("127.0.0.1:3333").unwrap(),
+            result.unwrap().rpc_addr
+        );
+
+        // Default test case
+        let config = case(&MIN_CONFIG_VARS).unwrap();
+        assert_eq!(config.rpc_addr, rpc_addr());
+    }
+
+    #[test]
+    fn test_fee_token_addr_is_validated() {
+        let result = case(&[
+            ("ETH_EXECUTION_RPC", "url"),
+            ("STARKNET_RPC", "url"),
+            ("FEE_TOKEN_ADDR", "invalid_value"),
+        ]);
+        assert!(result.is_err());
+
+        let result = case(&[
+            ("ETH_EXECUTION_RPC", "url"),
+            ("STARKNET_RPC", "url"),
+            ("FEE_TOKEN_ADDR", "1"),
+        ]);
+        assert!(result.is_ok());
+        assert_eq!(FieldElement::ONE, result.unwrap().fee_token_addr);
+
+        // Default test case
+        let config = case(&MIN_CONFIG_VARS).unwrap();
+        assert_eq!(config.fee_token_addr, fee_token_addr());
+    }
+}