diff --git a/src/proxy/anthropic.ts b/src/proxy/anthropic.ts
index 8d8965e..ba1874a 100644
--- a/src/proxy/anthropic.ts
+++ b/src/proxy/anthropic.ts
@@ -178,6 +178,62 @@ function setAnthropicBetaHeader(req: Request) {
   }
 }
 
+/**
+ * Adds web search tool for Claude-3.5 and Claude-3.7 models when enable_web_search is true
+ * 
+ * Supports all optional parameters documented in the Claude API:
+ * - max_uses: Limit the number of searches per request
+ * - allowed_domains: Only include results from these domains
+ * - blocked_domains: Never include results from these domains
+ * - user_location: Localize search results
+ */
+function addWebSearchTool(req: Request) {
+  // Check if this is a Claude model that supports web search and if web search is enabled
+  const supportsWebSearch = /^claude-3-(5|7)/.test(req.body.model);
+  const useWebSearch = supportsWebSearch && Boolean(req.body.enable_web_search);
+  
+  if (useWebSearch) {
+    // Create the base web search tool
+    const webSearchTool: any = {
+      'type': 'web_search_20250305',
+      'name': 'web_search',
+    };
+    
+    // Add optional parameters if provided by the client
+    
+    // max_uses: Limit the number of searches per request
+    if (typeof req.body.web_search_max_uses === 'number') {
+      webSearchTool.max_uses = req.body.web_search_max_uses;
+      delete req.body.web_search_max_uses;
+    }
+    
+    // allowed_domains: Only include results from these domains
+    if (Array.isArray(req.body.web_search_allowed_domains)) {
+      webSearchTool.allowed_domains = req.body.web_search_allowed_domains;
+      delete req.body.web_search_allowed_domains;
+    }
+    
+    // blocked_domains: Never include results from these domains
+    if (Array.isArray(req.body.web_search_blocked_domains)) {
+      webSearchTool.blocked_domains = req.body.web_search_blocked_domains;
+      delete req.body.web_search_blocked_domains;
+    }
+    
+    // user_location: Localize search results
+    if (req.body.web_search_user_location) {
+      webSearchTool.user_location = req.body.web_search_user_location;
+      delete req.body.web_search_user_location;
+    }
+    
+    // Add the web search tool to the tools array
+    req.body.tools = [...(req.body.tools || []), webSearchTool];
+  }
+  
+  // Delete custom parameters as they're not standard Claude API parameters
+  delete req.body.enable_web_search;
+  delete req.body.reasoning_effort;
+}
+
 function selectUpstreamPath(manager: ProxyReqManager) {
   const req = manager.request;
   const pathname = req.url.split("?")[0];
@@ -206,20 +262,26 @@ const anthropicProxy = createQueuedProxyMiddleware({
 
 const nativeAnthropicChatPreprocessor = createPreprocessorMiddleware(
   { inApi: "anthropic-chat", outApi: "anthropic-chat", service: "anthropic" },
-  { afterTransform: [setAnthropicBetaHeader] }
+  { afterTransform: [setAnthropicBetaHeader, addWebSearchTool] }
 );
 
-const nativeTextPreprocessor = createPreprocessorMiddleware({
-  inApi: "anthropic-text",
-  outApi: "anthropic-text",
-  service: "anthropic",
-});
+const nativeTextPreprocessor = createPreprocessorMiddleware(
+  {
+    inApi: "anthropic-text",
+    outApi: "anthropic-text",
+    service: "anthropic",
+  },
+  { afterTransform: [addWebSearchTool] }
+);
 
-const textToChatPreprocessor = createPreprocessorMiddleware({
-  inApi: "anthropic-text",
-  outApi: "anthropic-chat",
-  service: "anthropic",
-});
+const textToChatPreprocessor = createPreprocessorMiddleware(
+  {
+    inApi: "anthropic-text",
+    outApi: "anthropic-chat",
+    service: "anthropic",
+  },
+  { afterTransform: [addWebSearchTool] }
+);
 
 /**
  * Routes text completion prompts to anthropic-chat if they need translation
@@ -239,11 +301,14 @@ const oaiToTextPreprocessor = createPreprocessorMiddleware({
   service: "anthropic",
 });
 
-const oaiToChatPreprocessor = createPreprocessorMiddleware({
-  inApi: "openai",
-  outApi: "anthropic-chat",
-  service: "anthropic",
-});
+const oaiToChatPreprocessor = createPreprocessorMiddleware(
+  {
+    inApi: "openai",
+    outApi: "anthropic-chat",
+    service: "anthropic",
+  },
+  { afterTransform: [addWebSearchTool] }
+);
 
 /**
  * Routes an OpenAI prompt to either the legacy Claude text completion endpoint