agent2: Add now, grep, and web search tools (#35974)

Release Notes:

- N/A

---------

Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>
Co-authored-by: Antonio Scandurra <me@as-cii.com>

crates/agent2/src/tools/now_tool.rs

@@ -0,0 +1,66 @@
+use std::sync::Arc;
+
+use agent_client_protocol as acp;
+use anyhow::Result;
+use chrono::{Local, Utc};
+use gpui::{App, SharedString, Task};
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+
+use crate::{AgentTool, ToolCallEventStream};
+
+#[derive(Debug, Serialize, Deserialize, JsonSchema)]
+#[serde(rename_all = "snake_case")]
+pub enum Timezone {
+    /// Use UTC for the datetime.
+    Utc,
+    /// Use local time for the datetime.
+    Local,
+}
+
+/// Returns the current datetime in RFC 3339 format.
+/// Only use this tool when the user specifically asks for it or the current task would benefit from knowing the current datetime.
+#[derive(Debug, Serialize, Deserialize, JsonSchema)]
+pub struct NowToolInput {
+    /// The timezone to use for the datetime.
+    timezone: Timezone,
+}
+
+pub struct NowTool;
+
+impl AgentTool for NowTool {
+    type Input = NowToolInput;
+    type Output = String;
+
+    fn name(&self) -> SharedString {
+        "now".into()
+    }
+
+    fn kind(&self) -> acp::ToolKind {
+        acp::ToolKind::Other
+    }
+
+    fn initial_title(&self, _input: Result<Self::Input, serde_json::Value>) -> SharedString {
+        "Get current time".into()
+    }
+
+    fn run(
+        self: Arc<Self>,
+        input: Self::Input,
+        event_stream: ToolCallEventStream,
+        _cx: &mut App,
+    ) -> Task<Result<String>> {
+        let now = match input.timezone {
+            Timezone::Utc => Utc::now().to_rfc3339(),
+            Timezone::Local => Local::now().to_rfc3339(),
+        };
+        let content = format!("The current datetime is {now}.");
+
+        event_stream.update_fields(acp::ToolCallUpdateFields {
+            content: Some(vec![content.clone().into()]),
+            ..Default::default()
+        });
+
+        Task::ready(Ok(content))
+    }
+}