skip serializing the tool annotations if none, fixes mcp inspector

Author: abhay-agarwal

crates/rmcp/src/model/tool.rs

@@ -37,11 +37,13 @@ pub struct Tool {
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
 pub struct ToolAnnotations {
     /// A human-readable title for the tool.
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub title: Option<String>,
 
     /// If true, the tool does not modify its environment.
     ///
     /// Default: false
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub read_only_hint: Option<bool>,
 
     /// If true, the tool may perform destructive updates to its environment.
@@ -51,6 +53,7 @@ pub struct ToolAnnotations {
     ///
     /// Default: true
     /// A human-readable description of the tool's purpose.
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub destructive_hint: Option<bool>,
 
     /// If true, calling the tool repeatedly with the same arguments
@@ -59,6 +62,7 @@ pub struct ToolAnnotations {
     /// (This property is meaningful only when `readOnlyHint == false`)
     ///
     /// Default: false.
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub idempotent_hint: Option<bool>,
 
     /// If true, this tool may interact with an "open world" of external
@@ -67,6 +71,7 @@ pub struct ToolAnnotations {
     /// of a memory tool is not.
     ///
     /// Default: true
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub open_world_hint: Option<bool>,
 }