fix(model): add manual json schema implementation for NumberOrString

This commit adds a manual implementation of `JsonSchema` trait for the
`NumberOrString` enum to properly represent its union type nature in
JSON Schema. The schema now correctly specifies that the type can be
either a number or a string using the `oneOf` validation keyword.

Author: shorwood

crates/rmcp/src/model.rs

@@ -150,7 +150,6 @@ impl<'de> Deserialize<'de> for ProtocolVersion {
 }
 
 #[derive(Debug, Clone, Eq, PartialEq, Hash)]
-#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
 pub enum NumberOrString {
     Number(u32),
     String(Arc<str>),
@@ -203,6 +202,32 @@ impl<'de> Deserialize<'de> for NumberOrString {
     }
 }
 
+#[cfg(feature = "schemars")]
+impl schemars::JsonSchema for NumberOrString {
+    fn schema_name() -> String {
+        "NumberOrString".to_string()
+    }
+
+    fn json_schema(_: &mut schemars::SchemaGenerator) -> schemars::schema::Schema {
+        schemars::schema::Schema::Object(schemars::schema::SchemaObject {
+            subschemas: Some(Box::new(schemars::schema::SubschemaValidation {
+                one_of: Some(vec![
+                    schemars::schema::Schema::Object(schemars::schema::SchemaObject {
+                        instance_type: Some(schemars::schema::InstanceType::Number.into()),
+                        ..Default::default()
+                    }),
+                    schemars::schema::Schema::Object(schemars::schema::SchemaObject {
+                        instance_type: Some(schemars::schema::InstanceType::String.into()),
+                        ..Default::default()
+                    }),
+                ]),
+                ..Default::default()
+            })),
+            ..Default::default()
+        })
+    }
+}
+
 pub type RequestId = NumberOrString;
 
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Hash, Eq)]

crates/rmcp/tests/test_message_schema/client_json_rpc_message_schema.json

@@ -691,30 +691,10 @@
     "NumberOrString": {
       "oneOf": [
         {
-          "type": "object",
-          "required": [
-            "Number"
-          ],
-          "properties": {
-            "Number": {
-              "type": "integer",
-              "format": "uint32",
-              "minimum": 0.0
-            }
-          },
-          "additionalProperties": false
+          "type": "number"
         },
         {
-          "type": "object",
-          "required": [
-            "String"
-          ],
-          "properties": {
-            "String": {
-              "type": "string"
-            }
-          },
-          "additionalProperties": false
+          "type": "string"
         }
       ]
     },

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -966,30 +966,10 @@
     "NumberOrString": {
       "oneOf": [
         {
-          "type": "object",
-          "required": [
-            "Number"
-          ],
-          "properties": {
-            "Number": {
-              "type": "integer",
-              "format": "uint32",
-              "minimum": 0.0
-            }
-          },
-          "additionalProperties": false
+          "type": "number"
         },
         {
-          "type": "object",
-          "required": [
-            "String"
-          ],
-          "properties": {
-            "String": {
-              "type": "string"
-            }
-          },
-          "additionalProperties": false
+          "type": "string"
         }
       ]
     },