diff --git a/js/plugins/anthropic/src/parts/server_tool_use_part.ts b/js/plugins/anthropic/src/parts/server_tool_use_part.ts
index e2baeac61d..ce19571311 100644
--- a/js/plugins/anthropic/src/parts/server_tool_use_part.ts
+++ b/js/plugins/anthropic/src/parts/server_tool_use_part.ts
@@ -45,7 +45,6 @@ export const ServerToolUsePart: SupportedPart = {
             : baseName;
 
         return {
-          text: `[Anthropic server tool ${serverToolName}] input: ${JSON.stringify(contentBlock.input)}`,
           custom: {
             anthropicServerToolUse: {
               id: contentBlock.id,
@@ -70,7 +69,6 @@ export const ServerToolUsePart: SupportedPart = {
           );
         }
         return {
-          text: `[Anthropic server tool ${contentBlock.name}] input: ${JSON.stringify(contentBlock.input)}`,
           custom: {
             anthropicServerToolUse: {
               id: contentBlock.id,
diff --git a/js/plugins/anthropic/src/parts/web_search_tool_result_part.ts b/js/plugins/anthropic/src/parts/web_search_tool_result_part.ts
index a71dfd4dc2..186c730f72 100644
--- a/js/plugins/anthropic/src/parts/web_search_tool_result_part.ts
+++ b/js/plugins/anthropic/src/parts/web_search_tool_result_part.ts
@@ -77,7 +77,6 @@ function toWebSearchToolResultPart(params: {
 }): Part {
   const { toolUseId, content, type } = params;
   return {
-    text: `[Anthropic server tool result ${toolUseId}] ${JSON.stringify(content)}`,
     custom: {
       anthropicServerToolResult: {
         type,
diff --git a/js/plugins/anthropic/src/runner/beta.ts b/js/plugins/anthropic/src/runner/beta.ts
index 35f226cb6c..a8d5773b46 100644
--- a/js/plugins/anthropic/src/runner/beta.ts
+++ b/js/plugins/anthropic/src/runner/beta.ts
@@ -340,7 +340,11 @@ export class BetaRunner extends BaseRunner<BetaRunnerTypes> {
         .metadata as BetaMessageCreateParams['metadata'];
     }
     if (request.tools) {
-      body.tools = request.tools.map((tool) => this.toAnthropicTool(tool));
+      const configTools = (request.config?.tools as BetaTool[]) ?? [];
+      body.tools = [
+        ...configTools,
+        ...request.tools.map((tool) => this.toAnthropicTool(tool)),
+      ];
     }
     const thinkingConfig = this.toAnthropicThinkingConfig(
       request.config?.thinking
@@ -411,7 +415,11 @@ export class BetaRunner extends BaseRunner<BetaRunnerTypes> {
         .metadata as BetaMessageCreateParams['metadata'];
     }
     if (request.tools) {
-      body.tools = request.tools.map((tool) => this.toAnthropicTool(tool));
+      const configTools = (request.config?.tools as BetaTool[]) ?? [];
+      body.tools = [
+        ...configTools,
+        ...request.tools.map((tool) => this.toAnthropicTool(tool)),
+      ];
     }
     const thinkingConfig = this.toAnthropicThinkingConfig(
       request.config?.thinking
diff --git a/js/plugins/anthropic/src/runner/stable.ts b/js/plugins/anthropic/src/runner/stable.ts
index b5c6bef63f..b97aab4898 100644
--- a/js/plugins/anthropic/src/runner/stable.ts
+++ b/js/plugins/anthropic/src/runner/stable.ts
@@ -223,7 +223,11 @@ export class Runner extends BaseRunner<RunnerTypes> {
     }
 
     if (request.tools) {
-      body.tools = request.tools.map((tool) => this.toAnthropicTool(tool));
+      const configTools = (request.config?.tools as Tool[]) ?? [];
+      body.tools = [
+        ...configTools,
+        ...request.tools.map((tool) => this.toAnthropicTool(tool)),
+      ];
     }
     if (request.config?.topK !== undefined) {
       body.top_k = request.config.topK;
@@ -294,7 +298,11 @@ export class Runner extends BaseRunner<RunnerTypes> {
     }
 
     if (request.tools) {
-      body.tools = request.tools.map((tool) => this.toAnthropicTool(tool));
+      const configTools = (request.config?.tools as Tool[]) ?? [];
+      body.tools = [
+        ...configTools,
+        ...request.tools.map((tool) => this.toAnthropicTool(tool)),
+      ];
     }
     if (request.config?.topK !== undefined) {
       body.top_k = request.config.topK;
diff --git a/js/plugins/anthropic/src/types.ts b/js/plugins/anthropic/src/types.ts
index 9796d71c36..0e83f15f97 100644
--- a/js/plugins/anthropic/src/types.ts
+++ b/js/plugins/anthropic/src/types.ts
@@ -86,7 +86,7 @@ export const AnthropicBaseConfigSchema = GenerationCommonConfigSchema.extend({
     .optional(),
   /** Optional shorthand to pick API surface for this request. */
   apiVersion: z.enum(['stable', 'beta']).optional(),
-});
+}).passthrough();
 
 export type AnthropicBaseConfigSchemaType = typeof AnthropicBaseConfigSchema;
 
diff --git a/js/testapps/anthropic/package.json b/js/testapps/anthropic/package.json
index 08e1a0d2fd..6f2fd565a9 100644
--- a/js/testapps/anthropic/package.json
+++ b/js/testapps/anthropic/package.json
@@ -13,6 +13,7 @@
     "dev:stable:text-plain": "genkit start -- npx tsx --watch src/stable/text-plain.ts",
     "dev:stable:webp": "genkit start -- npx tsx --watch src/stable/webp.ts",
     "dev:stable:pdf": "genkit start -- npx tsx --watch src/stable/pdf.ts",
+    "dev:stable:web-search-tool": "genkit start -- npx tsx --watch src/stable/web-search-tool.ts",
     "genkit:dev": "cross-env GENKIT_ENV=dev npm run dev:stable",
     "genkit:start": "cross-env GENKIT_ENV=dev genkit start -- tsx --watch src/stable/basic.ts",
     "dev": "export GENKIT_RUNTIME_ID=$(openssl rand -hex 8) && node lib/stable/basic.js 2>&1"
diff --git a/js/testapps/anthropic/src/stable/web-search-tool.ts b/js/testapps/anthropic/src/stable/web-search-tool.ts
new file mode 100644
index 0000000000..c056f4c935
--- /dev/null
+++ b/js/testapps/anthropic/src/stable/web-search-tool.ts
@@ -0,0 +1,70 @@
+/**
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { anthropic } from '@genkit-ai/anthropic';
+import { genkit } from 'genkit';
+
+const ai = genkit({
+  plugins: [
+    // Configure the plugin with environment-driven API key
+    anthropic(),
+  ],
+});
+
+ai.defineFlow('anthropic-stable-web-search-tool', async () => {
+  const { text } = await ai.generate({
+    model: anthropic.model('claude-sonnet-4-5'),
+    prompt: 'What is the weather in Tokyo?',
+    config: {
+      tools: [
+        {
+          type: 'web_search_20250305',
+          name: 'web_search',
+        },
+      ],
+    },
+  });
+
+  return text;
+});
+
+ai.defineFlow(
+  'anthropic-stable-web-search-tool-stream',
+  async (_, { sendChunk }) => {
+    const { stream } = ai.generateStream({
+      model: anthropic.model('claude-sonnet-4-5'),
+      prompt: 'What is the weather in Tokyo?',
+      config: {
+        tools: [
+          {
+            type: 'web_search_20250305',
+            name: 'web_search',
+          },
+        ],
+      },
+    });
+
+    let response = '';
+    for await (const chunk of stream) {
+      if (chunk.text) {
+        response += chunk.text;
+        sendChunk(chunk.text);
+      }
+    }
+
+    return response;
+  }
+);