Drop redundant with_tools(declaration-only) calls in multi_client tests

The with_tool_handlers/with_tools merge means a single call now both
declares the tool and attaches the handler. The leftover second
with_tools([tool_definition]) call was overwriting the handler-bearing
tools list with declaration-only stubs, causing tool dispatch to break
and tests to time out.

Also conditionally import Tool in tool.rs (only used with derive/test
features) to silence unused-import lint under --features test-support.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: SteveSandersonMS

rust/src/tool.rs

@@ -21,9 +21,9 @@ use async_trait::async_trait;
 pub use schemars::JsonSchema;
 
 use crate::Error;
-use crate::types::{ToolBinaryResult, ToolInvocation, ToolResult, ToolResultExpanded};
 #[cfg(any(feature = "derive", test))]
 use crate::types::Tool;
+use crate::types::{ToolBinaryResult, ToolInvocation, ToolResult, ToolResultExpanded};
 
 /// Generate a JSON Schema [`Value`](serde_json::Value) from a Rust type.
 ///

rust/tests/e2e/multi_client.rs

@@ -41,7 +41,6 @@ async fn both_clients_see_tool_request_and_completion_events() {
                                 "MAGIC_",
                                 "_42",
                             )]))
-                            .with_tools([EchoTool::tool_definition("magic_number", "seed")])
                             .with_available_tools(["magic_number"]),
                     )
                     .await
@@ -293,7 +292,6 @@ async fn two_clients_register_different_tools_and_agent_uses_both() {
                                 "CITY_FOR_",
                                 "",
                             )]))
-                            .with_tools([EchoTool::tool_definition("city_lookup", "countryCode")])
                             .with_available_tools(["city_lookup", "currency_lookup"]),
                     )
                     .await
@@ -308,7 +306,6 @@ async fn two_clients_register_different_tools_and_agent_uses_both() {
                                 "CURRENCY_FOR_",
                                 "",
                             )]))
-                            .with_tools([EchoTool::tool_definition("currency_lookup", "countryCode")])
                             .with_available_tools(["city_lookup", "currency_lookup"]),
                     )
                     .await
@@ -361,7 +358,6 @@ async fn disconnecting_client_removes_its_tools() {
                                 "STABLE_",
                                 "",
                             )]))
-                            .with_tools([EchoTool::tool_definition("stable_tool", "input")])
                             .with_available_tools(["stable_tool", "ephemeral_tool"]),
                     )
                     .await
@@ -376,7 +372,6 @@ async fn disconnecting_client_removes_its_tools() {
                                 "EPHEMERAL_",
                                 "",
                             )]))
-                            .with_tools([EchoTool::tool_definition("ephemeral_tool", "input")])
                             .with_available_tools(["stable_tool", "ephemeral_tool"]),
                     )
                     .await