diff --git a/Cargo.lock b/Cargo.lock
index 20e7d9c..47196b3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -468,6 +468,10 @@ dependencies = [
 [[package]]
 name = "whoareyou-server"
 version = "0.1.0"
+dependencies = [
+ "serde",
+ "serde_json",
+]
 
 [[package]]
 name = "windows-link"
diff --git a/crates/server/Cargo.toml b/crates/server/Cargo.toml
index 207243b..4d5d24c 100644
--- a/crates/server/Cargo.toml
+++ b/crates/server/Cargo.toml
@@ -5,5 +5,7 @@ edition.workspace = true
 authors.workspace = true
 
 [dependencies]
+serde = { version = "1", features = ["derive"] }
 
 [dev-dependencies]
+serde_json = "1"
diff --git a/crates/server/src/lib.rs b/crates/server/src/lib.rs
index 272b9e3..65880be 100644
--- a/crates/server/src/lib.rs
+++ b/crates/server/src/lib.rs
@@ -1 +1 @@
-// modules added as they are implemented
+pub mod model;
diff --git a/crates/server/src/model.rs b/crates/server/src/model.rs
new file mode 100644
index 0000000..aa7a8dd
--- /dev/null
+++ b/crates/server/src/model.rs
@@ -0,0 +1,87 @@
+use std::collections::BTreeMap;
+
+use serde::Serialize;
+
+#[derive(Debug, Clone, PartialEq, Serialize)]
+pub struct Entry {
+    pub messages: Vec<String>,
+    pub history: Vec<String>,
+    pub comments: Vec<Comment>,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize)]
+pub struct Comment {
+    /// Unix epoch seconds, UTC.
+    pub timestamp: Option<i64>,
+    pub title: Option<String>,
+    pub message: String,
+}
+
+/// Per-provider outcome as exposed in the API (and cached).
+#[derive(Debug, Clone, PartialEq, Serialize)]
+#[serde(tag = "status", rename_all = "snake_case")]
+pub enum ProviderResult {
+    Ok { entry: Entry },
+    NoData,
+    FetchFailed,
+    ParseFailed,
+}
+
+/// A fetched HTTP response handed to a provider's `parse`.
+#[derive(Debug, Clone)]
+pub struct FetchedResponse {
+    pub status: u16,
+    pub body: String,
+}
+
+/// Outcome of a provider's `parse` call, before API mapping.
+#[derive(Debug)]
+pub enum ParseOutcome {
+    Ok(Entry),
+    NoData,
+    Failed(String),
+}
+
+#[derive(Debug, Serialize)]
+pub struct LookupResponse {
+    pub number: String,
+    pub results: BTreeMap<String, ProviderResult>,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn provider_result_serializes_to_api_shape() {
+        let ok = ProviderResult::Ok {
+            entry: Entry {
+                messages: vec![],
+                history: vec!["42 andra".to_string()],
+                comments: vec![Comment {
+                    timestamp: Some(1547746162),
+                    title: None,
+                    message: "Varmsälj".to_string(),
+                }],
+            },
+        };
+
+        let json = serde_json::to_value(&ok).unwrap();
+        assert_eq!(json["status"], "ok");
+        assert_eq!(json["entry"]["history"][0], "42 andra");
+        assert_eq!(json["entry"]["comments"][0]["timestamp"], 1547746162);
+
+        assert_eq!(
+            serde_json::to_value(&ProviderResult::NoData).unwrap()["status"],
+            "no_data"
+        );
+        assert_eq!(
+            serde_json::to_value(&ProviderResult::FetchFailed).unwrap()["status"],
+            "fetch_failed"
+        );
+        assert_eq!(
+            serde_json::to_value(&ProviderResult::ParseFailed).unwrap()["status"],
+            "parse_failed"
+        );
+    }
+}