diff --git a/plugins/permission-node/api-report.md b/plugins/permission-node/api-report.md
index 407ea3dc84..fe26dc2a1a 100644
--- a/plugins/permission-node/api-report.md
+++ b/plugins/permission-node/api-report.md
@@ -111,6 +111,6 @@ export type PolicyResult =
 
 // Warnings were encountered during analysis:
 //
-// src/integration/createPermissionIntegration.d.ts:38:5 - (ae-forgotten-export) The symbol "QueryType" needs to be exported by the entry point index.d.ts
-// src/integration/createPermissionIntegration.d.ts:39:5 - (ae-forgotten-export) The symbol "Conditions" needs to be exported by the entry point index.d.ts
+// src/integration/createPermissionIntegration.d.ts:28:5 - (ae-forgotten-export) The symbol "QueryType" needs to be exported by the entry point index.d.ts
+// src/integration/createPermissionIntegration.d.ts:29:5 - (ae-forgotten-export) The symbol "Conditions" needs to be exported by the entry point index.d.ts
 ```
diff --git a/plugins/permission-node/src/integration/createPermissionIntegration.ts b/plugins/permission-node/src/integration/createPermissionIntegration.ts
index 35d6f0da54..cbdcb72041 100644
--- a/plugins/permission-node/src/integration/createPermissionIntegration.ts
+++ b/plugins/permission-node/src/integration/createPermissionIntegration.ts
@@ -15,6 +15,7 @@
  */
 
 import express, { Response, Router } from 'express';
+import { z } from 'zod';
 import {
   AuthorizeResult,
   PermissionCondition,
@@ -24,6 +25,26 @@ import { PermissionRule } from '../types';
 import { conditionFor } from './conditionFor';
 import { applyConditions, mapConditions } from './util';
 
+const permissionCriteriaSchema: z.ZodSchema<
+  PermissionCriteria<PermissionCondition>
+> = z.lazy(() =>
+  z.union([
+    z.object({ anyOf: z.array(permissionCriteriaSchema) }),
+    z.object({ allOf: z.array(permissionCriteriaSchema) }),
+    z.object({ not: permissionCriteriaSchema }),
+    z.object({
+      rule: z.string(),
+      params: z.array(z.unknown()),
+    }),
+  ]),
+);
+
+const applyConditionsRequestSchema = z.object({
+  resourceRef: z.string(),
+  resourceType: z.string(),
+  conditions: permissionCriteriaSchema,
+});
+
 /**
  * A request to load the referenced resource and apply conditions, to finalize a conditional
  * authorization response.
@@ -105,15 +126,25 @@ export const createPermissionIntegration = <
         express.json(),
         async (
           req,
-          res: Response<{
-            result: Omit<AuthorizeResult, AuthorizeResult.CONDITIONAL>;
-          }>,
+          res: Response<
+            | {
+                result: Omit<AuthorizeResult, AuthorizeResult.CONDITIONAL>;
+              }
+            | string
+          >,
         ) => {
-          // TODO(authorization-framework): validate input
-          const body = req.body as ApplyConditionsRequest;
+          const parseResult = applyConditionsRequestSchema.safeParse(req.body);
+
+          if (!parseResult.success) {
+            return res.status(400).send(`Invalid request body.`);
+          }
+
+          const { data: body } = parseResult;
 
           if (body.resourceType !== resourceType) {
-            throw new Error(`Unexpected resource type: ${body.resourceType}`);
+            return res
+              .status(400)
+              .send(`Unexpected resource type: ${body.resourceType}.`);
           }
 
           const resource = await getResource(
@@ -122,7 +153,9 @@ export const createPermissionIntegration = <
           );
 
           if (!resource) {
-            return res.status(400).end();
+            return res
+              .status(400)
+              .send(`Resource for ref ${body.resourceRef} not found.`);
           }
 
           return res.status(200).json({