fix(shemars): use JSON Schema 2020-12 as Default Dialect

Author: jokemanfire

README.md

@@ -28,7 +28,8 @@ rmcp = { git = "https://github.com/modelcontextprotocol/rust-sdk", branch = "mai
 Basic dependencies:
 - [tokio required](https://github.com/tokio-rs/tokio)
 - [serde required](https://github.com/serde-rs/serde)
-
+Json Schema generation(Must follow the 2020-12 verison):
+- [shemars required](https://github.com/GREsau/schemars)
 
 
 ### Build a Client

crates/rmcp/Cargo.toml

@@ -143,7 +143,7 @@ schemars = ["dep:schemars"]
 
 [dev-dependencies]
 tokio = { version = "1", features = ["full"] }
-schemars = { version = "1.0", features = ["chrono04"] }
+schemars = { version = "1.1.0", features = ["chrono04"] }
 
 anyhow = "1.0"
 tracing-subscriber = { version = "0.3", features = [

crates/rmcp/src/handler/server/common.rs

@@ -11,10 +11,8 @@ use crate::{
 /// A shortcut for generating a JSON schema for a type.
 pub fn schema_for_type<T: JsonSchema>() -> JsonObject {
     // explicitly to align json schema version to official specifications.
-    // https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/schema/2025-03-26/schema.json
-    // TODO: update to 2020-12 waiting for the mcp spec update
-    let mut settings = SchemaSettings::draft07();
-    settings.transforms = vec![Box::new(schemars::transform::AddNullable::default())];
+    // refer to https://github.com/modelcontextprotocol/modelcontextprotocol/pull/655 for details.
+    let settings = SchemaSettings::draft2020_12();
     let generator = settings.into_generator();
     let schema = generator.into_root_schema_for::<T>();
     let object = serde_json::to_value(schema).expect("failed to serialize schema");