diff --git a/src/athlete_representatives/athlete_representative.dto.ts b/src/athlete_representatives/athlete_representative.dto.ts
index 7a26d98..c090eec 100644
--- a/src/athlete_representatives/athlete_representative.dto.ts
+++ b/src/athlete_representatives/athlete_representative.dto.ts
@@ -3,14 +3,14 @@ import { ApiProperty } from '@nestjs/swagger';
 export class AthleteRepresentative {
   @ApiProperty()
   id!: number;
-  @ApiProperty({ nullable: true })
+  @ApiProperty({ nullable: true, type: String })
   country!: string | null;
   @ApiProperty()
   firstname!: string;
   @ApiProperty()
   lastname!: string;
-  @ApiProperty({ nullable: true })
+  @ApiProperty({ nullable: true, type: String })
   email!: string | null;
-  @ApiProperty({ nullable: true })
+  @ApiProperty({ nullable: true, type: String })
   phone!: string | null;
 }
diff --git a/src/athletes/athlete.dto.ts b/src/athletes/athlete.dto.ts
index 0818f61..e4b4cb1 100644
--- a/src/athletes/athlete.dto.ts
+++ b/src/athletes/athlete.dto.ts
@@ -24,7 +24,7 @@ export class BaseAthlete {
 }
 
 export class BasePerformance extends Discipline {
-  @ApiProperty()
+  @ApiProperty({ nullable: true, type: Date })
   date!: Date | null;
   @ApiProperty()
   mark!: string;
@@ -32,6 +32,7 @@ export class BasePerformance extends Discipline {
     description:
       'Performance in milliseconds for track events and centimeters for field events',
     nullable: true,
+    type: Number,
   })
   performanceValue!: number | null;
   @ApiProperty()
diff --git a/src/competitions/competition.dto.ts b/src/competitions/competition.dto.ts
index a731db5..4d6c787 100644
--- a/src/competitions/competition.dto.ts
+++ b/src/competitions/competition.dto.ts
@@ -6,18 +6,18 @@ export class ContactPerson {
   email!: string;
   @ApiProperty()
   name!: string;
-  @ApiProperty()
+  @ApiProperty({ nullable: true, type: String })
   phone!: string | null;
   @ApiProperty()
   role!: string;
 }
 
 export class CompetitionOrganiserInfo {
-  @ApiProperty({ nullable: true })
+  @ApiProperty({ nullable: true, type: String })
   websiteUrl!: string | null;
-  @ApiProperty({ nullable: true })
+  @ApiProperty({ nullable: true, type: String })
   liveStreamUrl!: string | null;
-  @ApiProperty({ nullable: true })
+  @ApiProperty({ nullable: true, type: String })
   resultsUrl!: string | null;
   @ApiProperty({ type: [ContactPerson] })
   contactPersons!: ContactPerson[];
@@ -42,9 +42,9 @@ export class Competition {
   start!: Date;
   @ApiProperty()
   end!: Date;
-  @ApiProperty({ nullable: true })
+  @ApiProperty({ nullable: true, type: String })
   competitionGroup!: string | null;
-  @ApiProperty({ nullable: true })
+  @ApiProperty({ nullable: true, type: String })
   competitionSubgroup!: string | null;
   @ApiProperty()
   hasResults!: boolean;