diff --git a/src/proxy/middleware/request/preprocessors/sign-aws-request.ts b/src/proxy/middleware/request/preprocessors/sign-aws-request.ts
index 5a937bc..a564594 100644
--- a/src/proxy/middleware/request/preprocessors/sign-aws-request.ts
+++ b/src/proxy/middleware/request/preprocessors/sign-aws-request.ts
@@ -144,6 +144,8 @@ function applyAwsStrictValidation(req: Request): unknown {
         temperature: true,
         top_k: true,
         top_p: true,
+        tools: true,
+        tool_choice: true,
       })
         .strip()
         .parse(req.body);
diff --git a/src/proxy/middleware/request/preprocessors/sign-vertex-ai-request.ts b/src/proxy/middleware/request/preprocessors/sign-vertex-ai-request.ts
index afc6fb7..d95b1be 100644
--- a/src/proxy/middleware/request/preprocessors/sign-vertex-ai-request.ts
+++ b/src/proxy/middleware/request/preprocessors/sign-vertex-ai-request.ts
@@ -24,7 +24,6 @@ export const signGcpRequest: RequestPreprocessor = async (req) => {
   req.isStreaming = String(stream) === "true";
 
   // TODO: This should happen in transform-outbound-payload.ts
-  // TODO: Support tools
   let strippedParams: Record<string, unknown>;
   strippedParams = AnthropicV1MessagesSchema.pick({
     messages: true,
@@ -34,6 +33,8 @@ export const signGcpRequest: RequestPreprocessor = async (req) => {
     temperature: true,
     top_k: true,
     top_p: true,
+    tools: true,
+    tool_choice: true,
     stream: true,
   })
     .strip()
diff --git a/src/shared/api-schemas/anthropic.ts b/src/shared/api-schemas/anthropic.ts
index aa077f3..9bcd132 100644
--- a/src/shared/api-schemas/anthropic.ts
+++ b/src/shared/api-schemas/anthropic.ts
@@ -19,7 +19,12 @@ const AnthropicV1BaseSchema = z
     top_k: z.coerce.number().optional(),
     top_p: z.coerce.number().optional(),
     metadata: z.object({ user_id: z.string().optional() }).optional(),
+    tools: z.array(z.any()).optional(),
+    tool_choice: z.any().optional(),
   })
+  .omit(
+    Boolean(config.allowOpenAIToolUsage) ? {} : { tools: true, tool_choice: true }
+  )
   .strip();
 
 // https://docs.anthropic.com/claude/reference/complete_post [deprecated]
@@ -44,6 +49,18 @@ const AnthropicV1MessageMultimodalContentSchema = z.array(
         data: z.string(),
       }),
     }),
+    z.object({
+      type: z.literal("tool_use"),
+      id: z.string(),
+      name: z.string(),
+      input: z.object({}).passthrough(),
+    }),
+    z.object({
+      type: z.literal("tool_result"),
+      tool_use_id: z.string(),
+      is_error: z.boolean().optional(),
+      content: z.union([z.string(), z.object({}).passthrough()]).optional(),
+    }),
   ])
 );
 
diff --git a/src/shared/tokenization/claude.ts b/src/shared/tokenization/claude.ts
index 880db82..891ed2f 100644
--- a/src/shared/tokenization/claude.ts
+++ b/src/shared/tokenization/claude.ts
@@ -67,6 +67,9 @@ async function getTokenCountForMessages({
         case "image":
           numTokens += await getImageTokenCount(part.source.data);
           break;
+        case "tool_use":
+        case "tool_result":
+          break;
         default:
           throw new Error(`Unsupported Anthropic content type.`);
       }