diff --git a/packages/rs-dpp/src/data_contract/associated_token/token_perpetual_distribution/distribution_function/validation.rs b/packages/rs-dpp/src/data_contract/associated_token/token_perpetual_distribution/distribution_function/validation.rs
index c9738c71f1..0d7d782db5 100644
--- a/packages/rs-dpp/src/data_contract/associated_token/token_perpetual_distribution/distribution_function/validation.rs
+++ b/packages/rs-dpp/src/data_contract/associated_token/token_perpetual_distribution/distribution_function/validation.rs
@@ -1127,6 +1127,162 @@ mod tests {
                 .first_error()
                 .is_some());
         }
+
+        #[test]
+        fn test_step_decreasing_amount_invalid_zero_distribution_start() {
+            let dist = DistributionFunction::StepDecreasingAmount {
+                step_count: 10,
+                decrease_per_interval_numerator: 1,
+                decrease_per_interval_denominator: 2,
+                start_decreasing_offset: Some(0),
+                max_interval_count: None,
+                distribution_start_amount: 0,
+                trailing_distribution_interval_amount: 0,
+                min_value: Some(10),
+            };
+            let result = dist.validate(START_MOMENT, PlatformVersion::latest());
+            assert!(result
+                .expect("no error on test_step_decreasing_amount_invalid_zero_distribution_start")
+                .first_error()
+                .is_some());
+        }
+
+        #[test]
+        fn test_step_decreasing_amount_invalid_max_distribution_start() {
+            let dist = DistributionFunction::StepDecreasingAmount {
+                step_count: 10,
+                decrease_per_interval_numerator: 1,
+                decrease_per_interval_denominator: 2,
+                start_decreasing_offset: Some(0),
+                max_interval_count: None,
+                distribution_start_amount: MAX_DISTRIBUTION_PARAM + 1,
+                trailing_distribution_interval_amount: 0,
+                min_value: Some(10),
+            };
+            let result = dist.validate(START_MOMENT, PlatformVersion::latest());
+            assert!(result
+                .expect("no error on test_step_decreasing_amount_invalid_max_distribution_start")
+                .first_error()
+                .is_some());
+        }
+
+        #[test]
+        fn test_step_decreasing_amount_invalid_trailing_exceeds_start() {
+            let dist = DistributionFunction::StepDecreasingAmount {
+                step_count: 10,
+                decrease_per_interval_numerator: 1,
+                decrease_per_interval_denominator: 2,
+                start_decreasing_offset: Some(0),
+                max_interval_count: None,
+                distribution_start_amount: 100,
+                trailing_distribution_interval_amount: 101,
+                min_value: Some(10),
+            };
+            let result = dist.validate(START_MOMENT, PlatformVersion::latest());
+            assert!(result
+                .expect("no error on test_step_decreasing_amount_invalid_trailing_exceeds_start")
+                .first_error()
+                .is_some());
+        }
+
+        #[test]
+        fn test_step_decreasing_amount_invalid_max_interval_count_too_low() {
+            let dist = DistributionFunction::StepDecreasingAmount {
+                step_count: 10,
+                decrease_per_interval_numerator: 1,
+                decrease_per_interval_denominator: 2,
+                start_decreasing_offset: Some(0),
+                max_interval_count: Some(1),
+                distribution_start_amount: 100,
+                trailing_distribution_interval_amount: 0,
+                min_value: Some(10),
+            };
+            let result = dist.validate(START_MOMENT, PlatformVersion::latest());
+            assert!(result
+                .expect(
+                    "no error on test_step_decreasing_amount_invalid_max_interval_count_too_low"
+                )
+                .first_error()
+                .is_some());
+        }
+
+        #[test]
+        fn test_step_decreasing_amount_invalid_max_interval_count_too_high() {
+            let dist = DistributionFunction::StepDecreasingAmount {
+                step_count: 10,
+                decrease_per_interval_numerator: 1,
+                decrease_per_interval_denominator: 2,
+                start_decreasing_offset: Some(0),
+                max_interval_count: Some(1025),
+                distribution_start_amount: 100,
+                trailing_distribution_interval_amount: 0,
+                min_value: Some(10),
+            };
+            let result = dist.validate(START_MOMENT, PlatformVersion::latest());
+            assert!(result
+                .expect(
+                    "no error on test_step_decreasing_amount_invalid_max_interval_count_too_high"
+                )
+                .first_error()
+                .is_some());
+        }
+
+        #[test]
+        fn test_step_decreasing_amount_invalid_zero_numerator() {
+            let dist = DistributionFunction::StepDecreasingAmount {
+                step_count: 10,
+                decrease_per_interval_numerator: 0,
+                decrease_per_interval_denominator: 2,
+                start_decreasing_offset: Some(0),
+                max_interval_count: None,
+                distribution_start_amount: 100,
+                trailing_distribution_interval_amount: 0,
+                min_value: Some(10),
+            };
+            let result = dist.validate(START_MOMENT, PlatformVersion::latest());
+            assert!(result
+                .expect("no error on test_step_decreasing_amount_invalid_zero_numerator")
+                .first_error()
+                .is_some());
+        }
+
+        #[test]
+        fn test_step_decreasing_amount_invalid_numerator_gte_denominator() {
+            let dist = DistributionFunction::StepDecreasingAmount {
+                step_count: 10,
+                decrease_per_interval_numerator: 5,
+                decrease_per_interval_denominator: 5,
+                start_decreasing_offset: Some(0),
+                max_interval_count: None,
+                distribution_start_amount: 100,
+                trailing_distribution_interval_amount: 0,
+                min_value: Some(10),
+            };
+            let result = dist.validate(START_MOMENT, PlatformVersion::latest());
+            assert!(result
+                .expect("no error on test_step_decreasing_amount_invalid_numerator_gte_denominator")
+                .first_error()
+                .is_some());
+        }
+
+        #[test]
+        fn test_step_decreasing_amount_invalid_min_value_exceeds_start() {
+            let dist = DistributionFunction::StepDecreasingAmount {
+                step_count: 10,
+                decrease_per_interval_numerator: 1,
+                decrease_per_interval_denominator: 2,
+                start_decreasing_offset: Some(0),
+                max_interval_count: None,
+                distribution_start_amount: 50,
+                trailing_distribution_interval_amount: 0,
+                min_value: Some(100),
+            };
+            let result = dist.validate(START_MOMENT, PlatformVersion::latest());
+            assert!(result
+                .expect("no error on test_step_decreasing_amount_invalid_min_value_exceeds_start")
+                .first_error()
+                .is_some());
+        }
     }
     mod stepwise {
         use super::*;
diff --git a/packages/rs-dpp/src/data_contract/methods/validate_update/v0/mod.rs b/packages/rs-dpp/src/data_contract/methods/validate_update/v0/mod.rs
index 9657db4afa..5f34dc19df 100644
--- a/packages/rs-dpp/src/data_contract/methods/validate_update/v0/mod.rs
+++ b/packages/rs-dpp/src/data_contract/methods/validate_update/v0/mod.rs
@@ -612,6 +612,195 @@ mod tests {
             assert!(result.is_valid());
         }
 
+        #[test]
+        fn should_return_invalid_result_if_too_many_keywords() {
+            let platform_version = PlatformVersion::latest();
+
+            let old_data_contract = get_data_contract_fixture(
+                None,
+                IdentityNonce::default(),
+                platform_version.protocol_version,
+            )
+            .data_contract_owned();
+
+            let mut new_data_contract = old_data_contract.clone();
+            new_data_contract.set_version(old_data_contract.version() + 1);
+            new_data_contract.set_keywords((0..51).map(|i| format!("keyword{i:03}")).collect());
+
+            let result = old_data_contract
+                .validate_update_v0(&new_data_contract, &BlockInfo::default(), platform_version)
+                .expect("failed validate update");
+
+            assert_matches!(
+                result.errors.as_slice(),
+                [ConsensusError::BasicError(
+                    BasicError::TooManyKeywordsError(_)
+                )]
+            );
+        }
+
+        #[test]
+        fn should_return_invalid_result_if_keyword_too_short() {
+            let platform_version = PlatformVersion::latest();
+
+            let old_data_contract = get_data_contract_fixture(
+                None,
+                IdentityNonce::default(),
+                platform_version.protocol_version,
+            )
+            .data_contract_owned();
+
+            let mut new_data_contract = old_data_contract.clone();
+            new_data_contract.set_version(old_data_contract.version() + 1);
+            new_data_contract.set_keywords(vec!["ab".to_string()]);
+
+            let result = old_data_contract
+                .validate_update_v0(&new_data_contract, &BlockInfo::default(), platform_version)
+                .expect("failed validate update");
+
+            assert_matches!(
+                result.errors.as_slice(),
+                [ConsensusError::BasicError(
+                    BasicError::InvalidKeywordLengthError(_)
+                )]
+            );
+        }
+
+        #[test]
+        fn should_return_invalid_result_if_keyword_too_long() {
+            let platform_version = PlatformVersion::latest();
+
+            let old_data_contract = get_data_contract_fixture(
+                None,
+                IdentityNonce::default(),
+                platform_version.protocol_version,
+            )
+            .data_contract_owned();
+
+            let mut new_data_contract = old_data_contract.clone();
+            new_data_contract.set_version(old_data_contract.version() + 1);
+            new_data_contract.set_keywords(vec!["a".repeat(51)]);
+
+            let result = old_data_contract
+                .validate_update_v0(&new_data_contract, &BlockInfo::default(), platform_version)
+                .expect("failed validate update");
+
+            assert_matches!(
+                result.errors.as_slice(),
+                [ConsensusError::BasicError(
+                    BasicError::InvalidKeywordLengthError(_)
+                )]
+            );
+        }
+
+        #[test]
+        fn should_return_invalid_result_if_keyword_has_invalid_chars() {
+            let platform_version = PlatformVersion::latest();
+
+            let old_data_contract = get_data_contract_fixture(
+                None,
+                IdentityNonce::default(),
+                platform_version.protocol_version,
+            )
+            .data_contract_owned();
+
+            let mut new_data_contract = old_data_contract.clone();
+            new_data_contract.set_version(old_data_contract.version() + 1);
+            new_data_contract.set_keywords(vec!["hello world".to_string()]);
+
+            let result = old_data_contract
+                .validate_update_v0(&new_data_contract, &BlockInfo::default(), platform_version)
+                .expect("failed validate update");
+
+            assert_matches!(
+                result.errors.as_slice(),
+                [ConsensusError::BasicError(
+                    BasicError::InvalidKeywordCharacterError(_)
+                )]
+            );
+        }
+
+        #[test]
+        fn should_return_invalid_result_if_duplicate_keywords() {
+            let platform_version = PlatformVersion::latest();
+
+            let old_data_contract = get_data_contract_fixture(
+                None,
+                IdentityNonce::default(),
+                platform_version.protocol_version,
+            )
+            .data_contract_owned();
+
+            let mut new_data_contract = old_data_contract.clone();
+            new_data_contract.set_version(old_data_contract.version() + 1);
+            new_data_contract.set_keywords(vec!["keyword".to_string(), "keyword".to_string()]);
+
+            let result = old_data_contract
+                .validate_update_v0(&new_data_contract, &BlockInfo::default(), platform_version)
+                .expect("failed validate update");
+
+            assert_matches!(
+                result.errors.as_slice(),
+                [ConsensusError::BasicError(
+                    BasicError::DuplicateKeywordsError(_)
+                )]
+            );
+        }
+
+        #[test]
+        fn should_return_invalid_result_if_description_too_short() {
+            let platform_version = PlatformVersion::latest();
+
+            let old_data_contract = get_data_contract_fixture(
+                None,
+                IdentityNonce::default(),
+                platform_version.protocol_version,
+            )
+            .data_contract_owned();
+
+            let mut new_data_contract = old_data_contract.clone();
+            new_data_contract.set_version(old_data_contract.version() + 1);
+            new_data_contract.set_description(Some("ab".to_string()));
+
+            let result = old_data_contract
+                .validate_update_v0(&new_data_contract, &BlockInfo::default(), platform_version)
+                .expect("failed validate update");
+
+            assert_matches!(
+                result.errors.as_slice(),
+                [ConsensusError::BasicError(
+                    BasicError::InvalidDescriptionLengthError(_)
+                )]
+            );
+        }
+
+        #[test]
+        fn should_return_invalid_result_if_description_too_long() {
+            let platform_version = PlatformVersion::latest();
+
+            let old_data_contract = get_data_contract_fixture(
+                None,
+                IdentityNonce::default(),
+                platform_version.protocol_version,
+            )
+            .data_contract_owned();
+
+            let mut new_data_contract = old_data_contract.clone();
+            new_data_contract.set_version(old_data_contract.version() + 1);
+            new_data_contract.set_description(Some("a".repeat(101)));
+
+            let result = old_data_contract
+                .validate_update_v0(&new_data_contract, &BlockInfo::default(), platform_version)
+                .expect("failed validate update");
+
+            assert_matches!(
+                result.errors.as_slice(),
+                [ConsensusError::BasicError(
+                    BasicError::InvalidDescriptionLengthError(_)
+                )]
+            );
+        }
+
         //
         // ──────────────────────────────────────────────────────────────────────────
         //  Group‑related rules