[mcp] Support MCP Apps part 1. (#16082)

- [x] Add `mcpResource/read` method to read mcp resource.

codex-rs/app-server-protocol/src/protocol/common.rs

@@ -459,6 +459,11 @@ client_request_definitions! {
         response: v2::ListMcpServerStatusResponse,
     },
 
+    McpResourceRead => "mcpServer/resource/read" {
+        params: v2::McpResourceReadParams,
+        response: v2::McpResourceReadResponse,
+    },
+
     WindowsSandboxSetupStart => "windowsSandbox/setupStart" {
         params: v2::WindowsSandboxSetupStartParams,
         response: v2::WindowsSandboxSetupStartResponse,

codex-rs/app-server-protocol/src/protocol/v2.rs

@@ -29,6 +29,7 @@ use codex_protocol::config_types::WebSearchToolConfig;
 use codex_protocol::items::AgentMessageContent as CoreAgentMessageContent;
 use codex_protocol::items::TurnItem as CoreTurnItem;
 use codex_protocol::mcp::Resource as McpResource;
+pub use codex_protocol::mcp::ResourceContent as McpResourceContent;
 use codex_protocol::mcp::ResourceTemplate as McpResourceTemplate;
 use codex_protocol::mcp::Tool as McpTool;
 use codex_protocol::memory_citation::MemoryCitation as CoreMemoryCitation;
@@ -1984,6 +1985,22 @@ pub struct ListMcpServerStatusResponse {
     pub next_cursor: Option<String>,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct McpResourceReadParams {
+    pub thread_id: String,
+    pub server: String,
+    pub uri: String,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+#[ts(export_to = "v2/")]
+pub struct McpResourceReadResponse {
+    pub contents: Vec<McpResourceContent>,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 #[ts(export_to = "v2/")]