diff --git a/harvest-finance/backend/src/auth/auth.controller.ts b/harvest-finance/backend/src/auth/auth.controller.ts
index 1cd95640d..f86879e57 100644
--- a/harvest-finance/backend/src/auth/auth.controller.ts
+++ b/harvest-finance/backend/src/auth/auth.controller.ts
@@ -128,6 +128,10 @@ export class AuthController {
     status: 401,
     description: 'Invalid or expired refresh token',
   })
+  @ApiResponse({
+    status: 400,
+    description: 'Validation error — refresh_token field is missing or malformed',
+  })
   async refresh(
     @Body() refreshTokenDto: RefreshTokenDto,
   ): Promise<TokenResponseDto> {
diff --git a/harvest-finance/backend/src/auth/auth.service.spec.ts b/harvest-finance/backend/src/auth/auth.service.spec.ts
index 75a1f58e3..904432b0d 100644
--- a/harvest-finance/backend/src/auth/auth.service.spec.ts
+++ b/harvest-finance/backend/src/auth/auth.service.spec.ts
@@ -223,6 +223,7 @@ describe('AuthService', () => {
 
       expect(result).toHaveProperty('access_token');
       expect(result.access_token).toBe('new_access_token');
+      expect(result).toHaveProperty('token_type', 'Bearer');
     });
   });
 
diff --git a/harvest-finance/backend/src/auth/auth.service.ts b/harvest-finance/backend/src/auth/auth.service.ts
index 8e1c918f2..43911b05a 100644
--- a/harvest-finance/backend/src/auth/auth.service.ts
+++ b/harvest-finance/backend/src/auth/auth.service.ts
@@ -205,7 +205,7 @@ export class AuthService {
         },
       );
 
-      return { access_token: accessToken };
+      return { access_token: accessToken, token_type: 'Bearer' };
     } catch (error) {
       throw new UnauthorizedException('Invalid or expired refresh token');
     }
diff --git a/harvest-finance/backend/src/auth/dto/auth-response.dto.ts b/harvest-finance/backend/src/auth/dto/auth-response.dto.ts
index d8e7eec01..65bfe9add 100644
--- a/harvest-finance/backend/src/auth/dto/auth-response.dto.ts
+++ b/harvest-finance/backend/src/auth/dto/auth-response.dto.ts
@@ -76,9 +76,16 @@ export class TokenResponseDto {
   /** Freshly issued short-lived JWT access token. */
   @ApiProperty({
     example: 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...',
-    description: 'Access token (JWT)',
+    description: 'JWT access token to be sent as a Bearer token in the Authorization header',
   })
   access_token: string;
+
+  /** OAuth 2.0 token type. Always "Bearer" for this API. */
+  @ApiProperty({
+    example: 'Bearer',
+    description: 'Token type — always "Bearer". Prefix the access_token with this value in the Authorization header.',
+  })
+  token_type: string;
 }
 
 /** Response shape returned after a successful logout. */