diff --git a/crates/lmstudio/src/lmstudio.rs b/crates/lmstudio/src/lmstudio.rs
index 43c78115cdd4f517a51052991121620a0a93c363..ef2f7b6208f62e079609049b8eff83a80034741e 100644
--- a/crates/lmstudio/src/lmstudio.rs
+++ b/crates/lmstudio/src/lmstudio.rs
@@ -86,11 +86,12 @@ impl Model {
 }
 
 #[derive(Debug, Serialize, Deserialize)]
-#[serde(untagged)]
+#[serde(rename_all = "lowercase")]
 pub enum ToolChoice {
     Auto,
     Required,
     None,
+    #[serde(untagged)]
     Other(ToolDefinition),
 }
 
diff --git a/crates/mistral/src/mistral.rs b/crates/mistral/src/mistral.rs
index 55986e7e5bfd69ec91f11089753562e9e1984fcc..d6f62cfaa07bc211881817e6178a8673a9a670a6 100644
--- a/crates/mistral/src/mistral.rs
+++ b/crates/mistral/src/mistral.rs
@@ -286,12 +286,13 @@ pub enum Prediction {
 }
 
 #[derive(Debug, Serialize, Deserialize)]
-#[serde(rename_all = "snake_case")]
+#[serde(rename_all = "lowercase")]
 pub enum ToolChoice {
     Auto,
     Required,
     None,
     Any,
+    #[serde(untagged)]
     Function(ToolDefinition),
 }
 
diff --git a/crates/open_ai/src/open_ai.rs b/crates/open_ai/src/open_ai.rs
index f9a983b433b9d918424f9696269dd0bbd72adefd..279245c0b7d5a545a5d5c7725347f0b5153a4deb 100644
--- a/crates/open_ai/src/open_ai.rs
+++ b/crates/open_ai/src/open_ai.rs
@@ -269,11 +269,12 @@ pub struct Request {
 }
 
 #[derive(Debug, Serialize, Deserialize)]
-#[serde(untagged)]
+#[serde(rename_all = "lowercase")]
 pub enum ToolChoice {
     Auto,
     Required,
     None,
+    #[serde(untagged)]
     Other(ToolDefinition),
 }