diff --git a/supabase/functions/analyze-essay/index.ts b/supabase/functions/analyze-essay/index.ts
index eb5b1a5..c064af1 100644
--- a/supabase/functions/analyze-essay/index.ts
+++ b/supabase/functions/analyze-essay/index.ts
@@ -155,7 +155,52 @@ Responda em formato JSON seguindo exatamente esta estrutura:
           content: prompt
         }
       ],
-      response_format: { type: "json_object" }
+      response_format: { 
+        type: "json_schema",
+        json_schema: {
+          type: "object",
+          name: "EssayAnalysis",
+          schema: {
+            type: "object",
+            schema: {
+              type: "object",
+              additionalProperties: false,
+              properties: {
+                overall_score: { type: "number" },
+                feedback: {
+                  type: "object",
+                  additionalProperties: false,
+                  properties: {
+                    structure: { type: "string" },
+                    content: { type: "string" },
+                    language: { type: "string" }
+                  }
+                },
+                strengths: {
+                  type: "array",
+                  items: { type: "string" }
+                },
+                improvements: {
+                  type: "array", 
+                  items: { type: "string" }
+                },
+                suggestions: { type: "string" },
+                criteria_scores: {
+                  type: "object",
+                  additionalProperties: false,
+                  properties: {
+                    adequacy: { type: "number" },
+                    coherence: { type: "number" },
+                    cohesion: { type: "number" },
+                    vocabulary: { type: "number" },
+                    grammar: { type: "number" }
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
     });
 
     const analysis: EssayAnalysisResponse = JSON.parse(completion.choices[0].message.content)