diff --git a/packages/api/src/router/assistant-tools/shared.ts b/packages/api/src/router/assistant-tools/shared.ts
index dd2fbde..c819e7a 100644
--- a/packages/api/src/router/assistant-tools/shared.ts
+++ b/packages/api/src/router/assistant-tools/shared.ts
@@ -1,5 +1,6 @@
 import type { prisma } from "@capakraken/db";
 import type { PermissionKey, SystemRole } from "@capakraken/shared";
+import type { z } from "zod";
 import type { TRPCContext } from "../../trpc.js";
 
 export type ToolContext = {
@@ -29,6 +30,8 @@ export interface ToolDef {
     parameters: Record<string, unknown>;
   };
   access?: ToolAccessRequirements;
+  /** EGAI 4.3.1.2 — optional Zod schema to validate tool results before returning to the AI */
+  resultSchema?: z.ZodType;
 }
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -40,8 +43,6 @@ export function withToolAccess(
 ): ToolDef[] {
   return tools.map((tool) => ({
     ...tool,
-    ...(accessByName[tool.function.name]
-      ? { access: accessByName[tool.function.name] }
-      : {}),
+    ...(accessByName[tool.function.name] ? { access: accessByName[tool.function.name] } : {}),
   }));
 }