diff --git a/Cargo.lock b/Cargo.lock
index c4d9d26..8eb57c3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -154,6 +154,7 @@ dependencies = [
  "reqwest",
  "serde",
  "serde_json",
+ "thiserror 2.0.18",
  "tokio",
 ]
 
diff --git a/Cargo.toml b/Cargo.toml
index 743da72..e22d737 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,4 +11,5 @@ serde_json = "1"
 jsonwebtoken = { version = "10.3.0", features = ["aws_lc_rs"] }
 reqwest = { version = "0.13.2", features = ["json"] }
 once_cell = "1"
-dotenvy = "0.15"
\ No newline at end of file
+dotenvy = "0.15"
+thiserror = "2.0.18"
diff --git a/src/errors.rs b/src/errors.rs
new file mode 100644
index 0000000..4e45b57
--- /dev/null
+++ b/src/errors.rs
@@ -0,0 +1,12 @@
+// errors.rs
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum OllamaError {
+    #[error("prompt is required and cannot be empty")]
+    MissingPrompt,
+    #[error("model '{0}' is not available — run `ollama pull {0}` first")]
+    ModelNotFound(String),
+    #[error(transparent)]
+    Http(#[from] reqwest::Error),
+}
diff --git a/src/main.rs b/src/main.rs
index 11e70de..9f8d122 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,5 @@
 mod auth;
+mod errors;
 mod providers;
 mod routes;
 mod state;
diff --git a/src/providers/ollama.rs b/src/providers/ollama.rs
index 0cd93b1..9ecfca9 100644
--- a/src/providers/ollama.rs
+++ b/src/providers/ollama.rs
@@ -1,5 +1,7 @@
 use reqwest::Client;
-use serde_json::Value;
+use serde_json::{Value, json};
+
+use crate::errors::OllamaError;
 
 #[derive(Clone)]
 pub struct OllamaProvider {
@@ -15,11 +17,82 @@ impl OllamaProvider {
         }
     }
 
-    pub async fn list_models(&self) -> Result<Value, reqwest::Error> {
+    pub async fn list_models(&self) -> Result<Value, OllamaError> {
         let url = format!("{}/api/tags", self.base_url);
 
         let res = self.client.get(url).send().await?.json::<Value>().await?;
 
         Ok(res)
     }
+
+    pub async fn completions(&self, body: Value) -> Result<Value, OllamaError> {
+        // Validate prompt
+        let prompt = body
+            .get("prompt")
+            .and_then(|v| v.as_str())
+            .filter(|s| !s.trim().is_empty())
+            .ok_or(OllamaError::MissingPrompt)?;
+
+        let model = body
+            .get("model")
+            .and_then(|v| v.as_str())
+            .unwrap_or("llama3");
+
+        // Validate model availability
+        let available = self.list_models().await?; // Http error auto-converts via #[from]
+        let model_exists = available
+            .get("models")
+            .and_then(|m| m.as_array())
+            .map(|arr| {
+                arr.iter()
+                    .any(|m| m.get("name").and_then(|n| n.as_str()) == Some(model))
+            })
+            .unwrap_or(false);
+
+        if !model_exists {
+            return Err(OllamaError::ModelNotFound(model.to_string()));
+        }
+
+        // Build payload (now using validated locals)
+        let ollama_payload = json!({
+            "model":  model,
+            "prompt": prompt,
+            "stream": false,
+            "options": {
+                "temperature": body.get("temperature"),
+                "top_p":       body.get("top_p"),
+                "num_predict": body.get("max_tokens"),
+            }
+        });
+
+        let url = format!("{}/api/generate", self.base_url);
+        let res = self
+            .client
+            .post(&url)
+            .json(&ollama_payload)
+            .send()
+            .await?
+            .json::<Value>()
+            .await?;
+
+        Ok(json!({
+            "id":      "cmpl-ollama",
+            "object":  "text_completion",
+            "model":   res.get("model"),
+            "choices": [{
+                "text":          res.get("response"),
+                "index":         0,
+                "finish_reason": if res.get("done").and_then(|v| v.as_bool()).unwrap_or(false) {
+                    "stop"
+                } else {
+                    "length"
+                },
+            }],
+            "usage": {
+                "prompt_tokens":     res.get("prompt_eval_count"),
+                "completion_tokens": res.get("eval_count"),
+                "total_tokens":      null,
+            }
+        }))
+    }
 }
diff --git a/src/routes/v1/mod.rs b/src/routes/v1/mod.rs
index 0e98fa6..ea66a57 100644
--- a/src/routes/v1/mod.rs
+++ b/src/routes/v1/mod.rs
@@ -1,12 +1,12 @@
 pub mod models;
 
 use crate::auth::middleware::auth_middleware;
-use crate::routes::v1::models::list_models;
 use crate::state::app_state::AppState;
-use axum::{Router, middleware, routing::get};
+use axum::{Router, middleware, routing::get, routing::post};
 
 pub fn router() -> Router<AppState> {
     Router::new()
-        .route("/models", get(list_models))
+        .route("/models", get(models::list_models))
+        .route("/completions", post(models::completions))
         .layer(middleware::from_fn(auth_middleware))
 }
diff --git a/src/routes/v1/models.rs b/src/routes/v1/models.rs
index d2c966b..1eeafc9 100644
--- a/src/routes/v1/models.rs
+++ b/src/routes/v1/models.rs
@@ -1,6 +1,7 @@
 use axum::{Json, extract::State};
 use serde_json::Value;
 
+use crate::errors::OllamaError;
 use crate::state::app_state::AppState;
 
 pub async fn list_models(
@@ -14,3 +15,23 @@ pub async fn list_models(
         )),
     }
 }
+
+pub async fn completions(
+    State(state): State<AppState>,
+    Json(body): Json<Value>,
+) -> Result<Json<Value>, (axum::http::StatusCode, String)> {
+    match state.ollama.completions(body).await {
+        Ok(response) => Ok(Json(response)),
+        Err(OllamaError::MissingPrompt) => Err((
+            axum::http::StatusCode::BAD_REQUEST,
+            "prompt is required and cannot be empty".to_string(),
+        )),
+        Err(OllamaError::ModelNotFound(m)) => Err((
+            axum::http::StatusCode::UNPROCESSABLE_ENTITY,
+            format!("model '{m}' is not available — run `ollama pull {m}` first"),
+        )),
+        Err(OllamaError::Http(e)) => {
+            Err((axum::http::StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))
+        }
+    }
+}