docs: explain OAuth HTTP client setup (#918)

examples/clients/README.md

@@ -45,6 +45,7 @@ A client demonstrating how to authenticate with an MCP server using OAuth.
 
 - Starts a local HTTP server to handle OAuth callbacks
 - Initializes the OAuth state machine and begins the authorization flow
+- Shows how to pass a configured reqwest client for OAuth discovery, registration, token exchange, and refresh requests
 - Displays the authorization URL and waits for user authorization
 - Establishes an authorized connection to the MCP server using the acquired access token
 - Demonstrates how to use the authorized connection to retrieve available tools and prompts

examples/clients/src/auth/oauth_client.rs

@@ -1,4 +1,4 @@
-use std::{env, net::SocketAddr, sync::Arc};
+use std::{env, net::SocketAddr, sync::Arc, time::Duration};
 
 use anyhow::{Context, Result};
 use axum::{
@@ -115,8 +115,16 @@ async fn main() -> Result<()> {
         client_metadata_url
     );
 
+    // Configure the HTTP client used for OAuth discovery, registration, token
+    // exchange, and refresh. Customize this builder for proxies, TLS roots,
+    // default headers, or other reqwest settings required by your environment.
+    let oauth_http_client = reqwest::Client::builder()
+        .timeout(Duration::from_secs(30))
+        .build()
+        .context("Failed to build OAuth HTTP client")?;
+
     // initialize oauth state machine
-    let mut oauth_state = OAuthState::new(&server_url, None)
+    let mut oauth_state = OAuthState::new(&server_url, Some(oauth_http_client))
         .await
         .context("Failed to initialize oauth state machine")?;
     // use CIMD (SEP-991) with client metadata URL.