diff --git a/examples/hello-world.rs b/examples/hello-world.rs
index 10fb215..d5768b7 100644
--- a/examples/hello-world.rs
+++ b/examples/hello-world.rs
@@ -1,9 +1,27 @@
-use octox::{Error, Octox};
+use std::sync::Arc;
+
+use github_parts::event::Event;
+use serde_json::Value;
+
+use octox::{Error, Octox, Workflow, WorkflowError};
+
+#[derive(Debug)]
+struct HelloWorld;
+
+impl Workflow for HelloWorld {
+    fn process(&self, event: Event) -> Result<Value, WorkflowError> {
+        let body = format!("received {}", event).into();
+
+        println!("{}", &body);
+
+        Ok(body)
+    }
+}
 
 #[tokio::main]
 async fn main() -> Result<(), Error> {
     dotenv::dotenv().ok();
 
-    let octox = Octox::new();
+    let octox = Octox::new().workflow(Arc::new(HelloWorld))?;
     octox.serve().await
 }
diff --git a/src/auth.rs b/src/auth.rs
index 45fa7ab..ea3a0b4 100644
--- a/src/auth.rs
+++ b/src/auth.rs
@@ -5,51 +5,43 @@ use axum::Json;
 use hmac::{Hmac, Mac};
 use serde_json::json;
 use sha2::Sha256;
+use thiserror::Error;
 
 use crate::WebhookSecret;
 
 type HmacSha256 = Hmac<Sha256>;
 
+#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Error)]
 pub enum AuthError {
+    #[error("missing {0} header")]
     MissingHeader(String),
+    #[error("failed to initialize cryptographic key")]
     FailedHmacInitialization,
+    #[error("X-Hub-Signature-256 header has the wrong format")]
     WrongSignatureFormat,
+    #[error("failed to decode the X-Hub-Signature-256 header")]
     FailedDecodingSignature,
+    #[error("X-Hub-Signature-256 header is invalid")]
     InvalidSignature,
+    #[error("failed to deserialize the body based on the X-GitHub-Event header")]
     UnexpectedPayload,
 }
 
 impl IntoResponse for AuthError {
     fn into_response(self) -> Response {
-        let (status, error_message) = match self {
-            AuthError::MissingHeader(header) => (
-                StatusCode::BAD_REQUEST,
-                format!("missing {} header", header),
-            ),
-            AuthError::FailedHmacInitialization => (
-                StatusCode::INTERNAL_SERVER_ERROR,
-                "failed to initialize cryptographic key".into(),
-            ),
-            AuthError::WrongSignatureFormat => (
-                StatusCode::BAD_REQUEST,
-                "X-Hub-Signature-256 header must start with sha256=".into(),
-            ),
-            AuthError::FailedDecodingSignature => (
-                StatusCode::INTERNAL_SERVER_ERROR,
-                "failed to decode the X-Hub-Signature-256 header".into(),
-            ),
-            AuthError::InvalidSignature => (
-                StatusCode::UNAUTHORIZED,
-                "X-Hub-Signature-256 header is invalid".into(),
-            ),
-            AuthError::UnexpectedPayload => (
-                StatusCode::BAD_REQUEST,
-                "failed to deserialize the body based of the X-GitHub-Event header".into(),
-            ),
+        let message = self.to_string();
+
+        let status = match self {
+            AuthError::MissingHeader(_) => StatusCode::BAD_REQUEST,
+            AuthError::FailedHmacInitialization => StatusCode::INTERNAL_SERVER_ERROR,
+            AuthError::WrongSignatureFormat => StatusCode::BAD_REQUEST,
+            AuthError::FailedDecodingSignature => StatusCode::INTERNAL_SERVER_ERROR,
+            AuthError::InvalidSignature => StatusCode::UNAUTHORIZED,
+            AuthError::UnexpectedPayload => StatusCode::BAD_REQUEST,
         };
 
         let body = Json(json!({
-            "error": error_message,
+            "error": message,
         }));
 
         (status, body).into_response()
diff --git a/src/error.rs b/src/error.rs
index 689c266..d0e1ff8 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -2,10 +2,15 @@ use axum::http::StatusCode;
 use axum::response::{IntoResponse, Response};
 use thiserror::Error;
 
+use crate::auth::AuthError;
+use crate::workflow::WorkflowError;
+
 #[derive(Debug, Error)]
 pub enum Error {
     #[error("failed to call external API")]
     Api(#[from] reqwest::Error),
+    #[error(transparent)]
+    Auth(#[from] AuthError),
     #[error("failed to initialize the web framework")]
     Axum(#[from] hyper::Error),
     #[error("{0}")]
@@ -14,6 +19,8 @@ pub enum Error {
     Io(#[from] std::io::Error),
     #[error("failed to create JWT")]
     Jwt(#[from] jsonwebtoken::errors::Error),
+    #[error(transparent)]
+    Workflow(#[from] WorkflowError),
     #[error("{0}")]
     Unknown(String),
 }
diff --git a/src/lib.rs b/src/lib.rs
index f8f5d4b..c1ed003 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,6 +2,7 @@ use std::fmt::{Display, Formatter};
 use std::fs::File;
 use std::io::Read;
 use std::net::{IpAddr, Ipv4Addr, SocketAddr, TcpListener};
+use std::sync::Arc;
 
 use axum::routing::{get, post};
 use axum::{Extension, Router, Server};
@@ -10,11 +11,13 @@ use crate::routes::{health, webhook};
 
 pub use self::error::Error;
 pub use self::github::{AppId, GitHubHost, PrivateKey, WebhookSecret};
+pub use self::workflow::{Workflow, WorkflowError};
 
 mod auth;
 mod error;
 mod github;
 mod routes;
+mod workflow;
 
 #[derive(Debug)]
 pub struct Octox {
@@ -24,6 +27,7 @@ pub struct Octox {
     webhook_secret: Option<WebhookSecret>,
     socket_address: SocketAddr,
     tcp_listener: Option<TcpListener>,
+    workflow: Option<Arc<dyn Workflow>>,
 }
 
 impl Octox {
@@ -31,6 +35,11 @@ impl Octox {
         Self::default()
     }
 
+    pub fn workflow(mut self, workflow: Arc<dyn Workflow>) -> Result<Self, Error> {
+        self.workflow = Some(workflow);
+        Ok(self)
+    }
+
     pub fn github_host(mut self, github_host: String) -> Result<Self, Error> {
         self.github_host = GitHubHost::new(github_host);
         Ok(self)
@@ -67,6 +76,7 @@ impl Octox {
         let app = Router::new()
             .route("/", post(webhook))
             .route("/health", get(health))
+            .layer(self.workflow_extension()?)
             .layer(self.github_host_extension()?)
             .layer(self.app_id_extension()?)
             .layer(self.private_key_extension()?)
@@ -84,6 +94,14 @@ impl Octox {
         Ok(())
     }
 
+    fn workflow_extension(&self) -> Result<Extension<Arc<dyn Workflow>>, Error> {
+        if let Some(workflow) = &self.workflow {
+            return Ok(Extension(workflow.clone()));
+        }
+
+        Err(Error::Configuration("workflow must be set".into()))
+    }
+
     fn github_host_extension(&self) -> Result<Extension<GitHubHost>, Error> {
         Ok(Extension(self.github_host.clone()))
     }
@@ -166,6 +184,7 @@ impl Default for Octox {
             webhook_secret: None,
             socket_address,
             tcp_listener: None,
+            workflow: None,
         }
     }
 }
diff --git a/src/routes/webhook.rs b/src/routes/webhook.rs
index d1c462f..34365ff 100644
--- a/src/routes/webhook.rs
+++ b/src/routes/webhook.rs
@@ -1,23 +1,31 @@
+use std::sync::Arc;
+
 use axum::body::Bytes;
-use axum::http::{HeaderMap, StatusCode};
-use axum::Extension;
+use axum::http::HeaderMap;
+use axum::{Extension, Json};
 use github_parts::event::Event;
+use serde_json::Value;
 
 use crate::auth::{verify_signature, AuthError};
-use crate::WebhookSecret;
+use crate::error::Error;
+use crate::github::WebhookSecret;
+use crate::workflow::Workflow;
 
 pub async fn webhook(
     headers: HeaderMap,
     body: Bytes,
     Extension(webhook_secret): Extension<WebhookSecret>,
-) -> Result<StatusCode, AuthError> {
+    Extension(workflow): Extension<Arc<dyn Workflow>>,
+) -> Result<Json<Value>, Error> {
     let signature = get_signature(&headers)?;
     verify_signature(&body, &signature, &webhook_secret)?;
 
     let event_type = get_event(&headers)?;
-    let _event = deserialize_event(&event_type, &body)?;
+    let event = deserialize_event(&event_type, &body)?;
+
+    let body = workflow.process(event)?;
 
-    Ok(StatusCode::OK)
+    Ok(Json(body))
 }
 
 fn get_signature(headers: &HeaderMap) -> Result<String, AuthError> {
diff --git a/src/workflow.rs b/src/workflow.rs
new file mode 100644
index 0000000..4278904
--- /dev/null
+++ b/src/workflow.rs
@@ -0,0 +1,26 @@
+use axum::http::StatusCode;
+use axum::response::{IntoResponse, Response};
+use std::fmt::Debug;
+
+use github_parts::event::Event;
+use thiserror::Error;
+
+pub trait Workflow: Debug + Sync + Send {
+    fn process(&self, event: Event) -> Result<serde_json::Value, WorkflowError>;
+}
+
+#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Error)]
+pub enum WorkflowError {
+    #[error("{0}")]
+    Unknown(String),
+}
+
+impl IntoResponse for WorkflowError {
+    fn into_response(self) -> Response {
+        match self {
+            WorkflowError::Unknown(error) => {
+                (StatusCode::INTERNAL_SERVER_ERROR, error).into_response()
+            }
+        }
+    }
+}
diff --git a/tests/health.rs b/tests/health.rs
index 9a77f45..96a0407 100644
--- a/tests/health.rs
+++ b/tests/health.rs
@@ -1,10 +1,15 @@
-use mockito::mock;
 use std::net::{SocketAddr, TcpListener};
+use std::sync::Arc;
 
+use mockito::mock;
 use reqwest::Client;
 
 use octox::{Error, Octox};
 
+use self::workflow::HelloWorld;
+
+mod workflow;
+
 #[tokio::test]
 async fn health_returns_ok() -> Result<(), Error> {
     dotenv::dotenv().ok();
@@ -16,9 +21,10 @@ async fn health_returns_ok() -> Result<(), Error> {
 
     let octox = Octox::new()
         .tcp_listener(listener)?
-        .github_host(mockito::server_url())?
         .app_id(1)?
-        .private_key(include_str!("fixtures/private-key.pem"))?;
+        .github_host(mockito::server_url())?
+        .private_key(include_str!("fixtures/private-key.pem"))?
+        .workflow(Arc::new(HelloWorld))?;
 
     tokio::spawn(async move {
         octox.serve().await.unwrap();
@@ -46,7 +52,8 @@ async fn health_returns_error() -> Result<(), Error> {
 
     let octox = Octox::new()
         .tcp_listener(listener)?
-        .github_host(mockito::server_url())?;
+        .github_host(mockito::server_url())?
+        .workflow(Arc::new(HelloWorld))?;
 
     tokio::spawn(async move {
         octox.serve().await.unwrap();
diff --git a/tests/webhook.rs b/tests/webhook.rs
index 1b16907..f71ad63 100644
--- a/tests/webhook.rs
+++ b/tests/webhook.rs
@@ -1,9 +1,15 @@
-use reqwest::Client;
 use std::fs::read;
 use std::net::{SocketAddr, TcpListener};
+use std::sync::Arc;
+
+use reqwest::Client;
 
 use octox::{Error, Octox};
 
+use self::workflow::HelloWorld;
+
+mod workflow;
+
 #[tokio::test]
 async fn webhook_accepts_valid_signature() -> Result<(), Error> {
     dotenv::dotenv().ok();
@@ -14,7 +20,8 @@ async fn webhook_accepts_valid_signature() -> Result<(), Error> {
     let octox = Octox::new()
         .tcp_listener(listener)?
         .github_host(mockito::server_url())?
-        .webhook_secret("secret")?;
+        .webhook_secret("secret")?
+        .workflow(Arc::new(HelloWorld))?;
 
     tokio::spawn(async move {
         octox.serve().await.unwrap();
@@ -37,7 +44,10 @@ async fn webhook_accepts_valid_signature() -> Result<(), Error> {
         .send()
         .await?;
 
-    assert_eq!("", response.text().await.unwrap());
+    assert_eq!(
+        "\"received unsupported event\"",
+        response.text().await.unwrap()
+    );
     Ok(())
 }
 
@@ -51,7 +61,8 @@ async fn webhook_requires_signature() -> Result<(), Error> {
     let octox = Octox::new()
         .tcp_listener(listener)?
         .github_host(mockito::server_url())?
-        .webhook_secret("secret")?;
+        .webhook_secret("secret")?
+        .workflow(Arc::new(HelloWorld))?;
 
     tokio::spawn(async move {
         octox.serve().await.unwrap();
@@ -87,7 +98,8 @@ async fn webhook_rejects_invalid_signature() -> Result<(), Error> {
     let octox = Octox::new()
         .tcp_listener(listener)?
         .github_host(mockito::server_url())?
-        .webhook_secret("secret")?;
+        .webhook_secret("secret")?
+        .workflow(Arc::new(HelloWorld))?;
 
     tokio::spawn(async move {
         octox.serve().await.unwrap();
diff --git a/tests/workflow.rs b/tests/workflow.rs
new file mode 100644
index 0000000..e737e51
--- /dev/null
+++ b/tests/workflow.rs
@@ -0,0 +1,13 @@
+use github_parts::event::Event;
+use serde_json::Value;
+
+use octox::{Workflow, WorkflowError};
+
+#[derive(Debug)]
+pub struct HelloWorld;
+
+impl Workflow for HelloWorld {
+    fn process(&self, event: Event) -> Result<Value, WorkflowError> {
+        Ok(format!("received {}", event).into())
+    }
+}