diff --git a/Cargo.lock b/Cargo.lock
index 6a07fe1..3331e72 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -36,6 +36,7 @@ checksum = "3a6c9af12842a67734c9a2e355436e5d03b22383ed60cf13cd0c18fbfe3dcbcf"
 dependencies = [
  "async-trait",
  "axum-core",
+ "axum-macros",
  "bytes",
  "futures-util",
  "http",
@@ -83,6 +84,18 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "axum-macros"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "00c055ee2d014ae5981ce1016374e8213682aa14d9bf40e48ab48b5f3ef20eaa"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "backtrace"
 version = "0.3.72"
@@ -182,6 +195,12 @@ version = "0.29.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "40ecd4077b5ae9fd2e9e169b102c6c330d0605168eb0e8bf79952b256dbefffd"
 
+[[package]]
+name = "heck"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95505c38b4572b2d910cecb0281560f54b440a19336cbbcb27bf6ce6adc6f5a8"
+
 [[package]]
 name = "hermit-abi"
 version = "0.3.9"
diff --git a/Cargo.toml b/Cargo.toml
index c1b4ff0..85525fb 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,7 @@ tokio-util = { version = "0.7.11", features = ["io"] }
 # Serialization / Deserialization
 serde = { version = "1.0.203", features = ["derive", "rc"] }
 # API
-axum = "0.7.5"
+axum = { version = "0.7.5", features = ["macros"] }
 tower-http = { version = "0.5.2", features = ["cors", "trace"] }
 # Logging
 tracing = "0.1.40"
diff --git a/src/main.rs b/src/main.rs
index e7ce8df..3340dd4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,7 +6,7 @@ use tower_http::trace;
 use tower_http::trace::TraceLayer;
 use tracing::Level;
 
-use crate::routing::{index, simplify, table};
+use crate::routing::routes::*;
 
 mod expressions;
 mod parsing;
@@ -28,7 +28,8 @@ async fn main() {
 
     let routes = simplify::router()
         .merge(table::router())
-        .merge(index::router());
+        .merge(index::router())
+        .merge(util::router());
 
     let app = routes
         .layer(CorsLayer::new().allow_origin(Any))
diff --git a/src/routing/mod.rs b/src/routing/mod.rs
index 30367ea..0d75636 100644
--- a/src/routing/mod.rs
+++ b/src/routing/mod.rs
@@ -1,5 +1,3 @@
-pub(crate) mod simplify;
-pub(crate) mod table;
-pub(crate) mod index;
 pub(crate) mod response;
-mod error;
\ No newline at end of file
+mod error;
+pub(crate) mod routes;
\ No newline at end of file
diff --git a/src/routing/response.rs b/src/routing/response.rs
index 222c563..e8269b6 100644
--- a/src/routing/response.rs
+++ b/src/routing/response.rs
@@ -1,6 +1,6 @@
 use axum::Json;
 use axum::response::{IntoResponse, Response};
-use serde::Serialize;
+use serde::{Deserialize, Serialize};
 
 use crate::expressions::expression::Expression;
 use crate::expressions::simplify::Law;
@@ -60,4 +60,16 @@ impl IntoResponse for SimplifyResponse {
     fn into_response(self) -> Response {
         BaseResponse::create(self)
     }
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct IsLegalResponse {
+    pub is_legal: bool,
+}
+
+impl IntoResponse for IsLegalResponse {
+    fn into_response(self) -> Response {
+        BaseResponse::create(self)
+    }
 }
\ No newline at end of file
diff --git a/src/routing/index.rs b/src/routing/routes/index.rs
similarity index 100%
rename from src/routing/index.rs
rename to src/routing/routes/index.rs
diff --git a/src/routing/routes/mod.rs b/src/routing/routes/mod.rs
new file mode 100644
index 0000000..e476db7
--- /dev/null
+++ b/src/routing/routes/mod.rs
@@ -0,0 +1,7 @@
+pub(crate) mod index;
+
+pub(crate) mod simplify;
+
+pub(crate) mod table;
+
+pub(crate) mod util;
diff --git a/src/routing/simplify.rs b/src/routing/routes/simplify.rs
similarity index 100%
rename from src/routing/simplify.rs
rename to src/routing/routes/simplify.rs
diff --git a/src/routing/table.rs b/src/routing/routes/table.rs
similarity index 63%
rename from src/routing/table.rs
rename to src/routing/routes/table.rs
index a213290..464dd22 100644
--- a/src/routing/table.rs
+++ b/src/routing/routes/table.rs
@@ -1,3 +1,4 @@
+use axum::body::Body;
 use axum::response::Response;
 use axum::Router;
 use axum::routing::post;
@@ -9,6 +10,7 @@ pub fn router() -> Router<()> {
         )
 }
 
-async fn table() -> Response {
+// TODO Json Deserialize not working on Axum? Manually parse the body?
+async fn table(body: Body) -> Response {
     unimplemented!()
 }
diff --git a/src/routing/routes/util.rs b/src/routing/routes/util.rs
new file mode 100644
index 0000000..086b946
--- /dev/null
+++ b/src/routing/routes/util.rs
@@ -0,0 +1,20 @@
+use axum::extract::Path;
+use axum::response::{IntoResponse, Response};
+use axum::Router;
+use axum::routing::get;
+
+use crate::expressions::expression::Expression;
+use crate::routing::error::{Error, ErrorKind};
+use crate::routing::response::IsLegalResponse;
+
+pub fn router() -> Router<()> {
+    Router::new()
+        .route("/is-legal/:exp", get(is_legal))
+}
+
+async fn is_legal(Path(path): Path<String>) -> Response {
+    match Expression::try_from(path.as_str()) {
+        Ok(_) => IsLegalResponse { is_legal: true }.into_response(),
+        Err(error) => Error::new(error.to_string(), ErrorKind::InvalidExpression).into_response()
+    }
+}