diff --git a/crates/api-types/src/lib.rs b/crates/api-types/src/lib.rs
index e69de29..116da0f 100644
--- a/crates/api-types/src/lib.rs
+++ b/crates/api-types/src/lib.rs
@@ -0,0 +1,2 @@
+pub mod requests;
+pub mod responses;
diff --git a/crates/api-types/src/requests.rs b/crates/api-types/src/requests.rs
new file mode 100644
index 0000000..c521dcc
--- /dev/null
+++ b/crates/api-types/src/requests.rs
@@ -0,0 +1,71 @@
+use serde::Deserialize;
+use uuid::Uuid;
+
+#[derive(Deserialize)]
+pub struct RegisterRequest {
+    pub username: String,
+    pub email: String,
+    pub password: String,
+}
+
+#[derive(Deserialize)]
+pub struct LoginRequest {
+    pub email: String,
+    pub password: String,
+}
+
+#[derive(Deserialize)]
+pub struct CreateThoughtRequest {
+    pub content: String,
+    pub in_reply_to_id: Option<Uuid>,
+    pub visibility: Option<String>,
+    pub content_warning: Option<String>,
+    pub sensitive: Option<bool>,
+}
+
+#[derive(Deserialize)]
+pub struct EditThoughtRequest {
+    pub content: String,
+}
+
+#[derive(Deserialize)]
+pub struct UpdateProfileRequest {
+    pub display_name: Option<String>,
+    pub bio: Option<String>,
+    pub avatar_url: Option<String>,
+    pub header_url: Option<String>,
+    pub custom_css: Option<String>,
+}
+
+#[derive(Deserialize)]
+pub struct SetTopFriendsRequest {
+    pub friend_ids: Vec<Uuid>,
+}
+
+#[derive(Deserialize)]
+pub struct CreateApiKeyRequest {
+    pub name: String,
+}
+
+#[derive(Deserialize)]
+pub struct PaginationQuery {
+    pub page: Option<u64>,
+    pub per_page: Option<u64>,
+}
+
+impl PaginationQuery {
+    pub fn page(&self) -> u64 {
+        self.page.unwrap_or(1).max(1)
+    }
+
+    pub fn per_page(&self) -> u64 {
+        self.per_page.unwrap_or(20).min(100)
+    }
+}
+
+#[derive(Deserialize)]
+pub struct SearchQuery {
+    pub q: String,
+    pub page: Option<u64>,
+    pub per_page: Option<u64>,
+}
diff --git a/crates/api-types/src/responses.rs b/crates/api-types/src/responses.rs
new file mode 100644
index 0000000..bcadb60
--- /dev/null
+++ b/crates/api-types/src/responses.rs
@@ -0,0 +1,69 @@
+use chrono::{DateTime, Utc};
+use serde::Serialize;
+use uuid::Uuid;
+
+#[derive(Serialize)]
+pub struct AuthResponse {
+    pub token: String,
+    pub user: UserResponse,
+}
+
+#[derive(Serialize, Clone)]
+pub struct UserResponse {
+    pub id: Uuid,
+    pub username: String,
+    pub display_name: Option<String>,
+    pub bio: Option<String>,
+    pub avatar_url: Option<String>,
+    pub header_url: Option<String>,
+    pub local: bool,
+    pub created_at: DateTime<Utc>,
+}
+
+#[derive(Serialize, Clone)]
+pub struct ThoughtResponse {
+    pub id: Uuid,
+    pub content: String,
+    pub author: UserResponse,
+    pub in_reply_to_id: Option<Uuid>,
+    pub visibility: String,
+    pub content_warning: Option<String>,
+    pub sensitive: bool,
+    pub like_count: i64,
+    pub boost_count: i64,
+    pub reply_count: i64,
+    pub liked_by_viewer: bool,
+    pub boosted_by_viewer: bool,
+    pub created_at: DateTime<Utc>,
+    pub updated_at: Option<DateTime<Utc>>,
+}
+
+#[derive(Serialize)]
+pub struct PagedResponse<T: Serialize> {
+    pub items: Vec<T>,
+    pub total: i64,
+    pub page: u64,
+    pub per_page: u64,
+}
+
+#[derive(Serialize)]
+pub struct ApiKeyResponse {
+    pub id: Uuid,
+    pub name: String,
+    pub created_at: DateTime<Utc>,
+}
+
+#[derive(Serialize)]
+pub struct NotificationResponse {
+    pub id: Uuid,
+    pub notification_type: String,
+    pub from_user: Option<UserResponse>,
+    pub thought_id: Option<Uuid>,
+    pub read: bool,
+    pub created_at: DateTime<Utc>,
+}
+
+#[derive(Serialize)]
+pub struct ErrorResponse {
+    pub error: String,
+}