diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2aef71158..a6ec775c6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,14 +26,6 @@ jobs:
     strategy:
       matrix:
         entry:
-          - { ruby: '3.1', grape: '1.8.0' }
-          - { ruby: '3.2', grape: '1.8.0' }
-          - { ruby: '3.3', grape: '1.8.0' }
-          - { ruby: '3.4', grape: '1.8.0' }
-          - { ruby: '3.1', grape: '2.0.0' }
-          - { ruby: '3.2', grape: '2.0.0' }
-          - { ruby: '3.3', grape: '2.0.0' }
-          - { ruby: '3.4', grape: '2.0.0' }
           - { ruby: '3.1', grape: '2.1.3' }
           - { ruby: '3.2', grape: '2.1.3' }
           - { ruby: '3.3', grape: '2.1.3' }
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 811dd12a2..587c88dc3 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -6,6 +6,14 @@
 # Note that changes in the inspected code, or installation of new
 # versions of RuboCop, may require this file to be generated again.
 
+# Offense count: 4
+# Configuration parameters: Severity.
+Style/OneClassPerFile:
+  Exclude:
+    - 'lib/grape-swagger.rb'
+    - 'spec/support/empty_model_parser.rb'
+    - 'spec/swagger_v2/guarded_endpoint_spec.rb'
+
 # Offense count: 1
 # Configuration parameters: Severity, Include.
 # Include: **/*.gemspec
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 428ddb86e..004cc8ba7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,7 +6,7 @@
 
 #### Fixes
 
-* Your contribution here.
+* [#977](https://github.com/ruby-grape/grape-swagger/issues/977): Pass keyword arguments to `desc` to fix deprecation warning from Grape - [@numbata](https://github.com/numbata).
 
 ### 2.1.4 (2026-02-02)
 
diff --git a/grape-swagger.gemspec b/grape-swagger.gemspec
index d88943efa..ce9d6b7fe 100644
--- a/grape-swagger.gemspec
+++ b/grape-swagger.gemspec
@@ -15,7 +15,7 @@ Gem::Specification.new do |s|
   s.metadata['rubygems_mfa_required'] = 'true'
 
   s.required_ruby_version = '>= 3.1'
-  s.add_dependency 'grape', '>= 1.7', '< 4.0'
+  s.add_dependency 'grape', '>= 2.1', '< 4.0'
 
   s.files = Dir['lib/**/*', '*.md', 'LICENSE.txt', 'grape-swagger.gemspec']
   s.require_paths = ['lib']
diff --git a/lib/grape-swagger/doc_methods.rb b/lib/grape-swagger/doc_methods.rb
index 9e22499d7..dd727a825 100644
--- a/lib/grape-swagger/doc_methods.rb
+++ b/lib/grape-swagger/doc_methods.rb
@@ -93,7 +93,7 @@ def setup(options)
 
       setup_formatter(options[:format])
 
-      desc api_doc.delete(:desc), api_doc
+      desc api_doc.delete(:desc), **api_doc
 
       instance_eval(guard) unless guard.nil?
 
@@ -105,7 +105,7 @@ def setup(options)
           .output_path_definitions(target_class.combined_namespace_routes, self, target_class, options)
       end
 
-      desc specific_api_doc.delete(:desc), { params: specific_api_doc.delete(:params) || {}, **specific_api_doc }
+      desc specific_api_doc.delete(:desc), params: specific_api_doc.delete(:params) || {}, **specific_api_doc
 
       params do
         requires :name, type: String, desc: 'Resource name of mounted API'
diff --git a/lib/grape-swagger/request_param_parsers/route.rb b/lib/grape-swagger/request_param_parsers/route.rb
index d3d27d20c..95dc1ffb1 100644
--- a/lib/grape-swagger/request_param_parsers/route.rb
+++ b/lib/grape-swagger/request_param_parsers/route.rb
@@ -19,8 +19,9 @@ def parse
         stackable_values = route.app&.inheritable_setting&.namespace_stackable
 
         path_params = build_path_params(stackable_values)
+        variant_types = collect_variant_types(stackable_values)
 
-        fulfill_params(path_params)
+        fulfill_params(path_params, variant_types)
       end
 
       private
@@ -47,7 +48,33 @@ def fetch_inherited_params(stackable_values)
         end
       end
 
-      def fulfill_params(path_params)
+      # In Grape >= 3.3 `type: [A, B]` is wrapped in VariantCollectionCoercer and
+      # Grape's documentation pipeline serialises it via `#to_s`, so the original
+      # type list is lost in route.params. The live coercer is still reachable
+      # through the CoerceValidator's @converter, so we rebuild a name => types
+      # map and restore it in fulfill_params.
+      def collect_variant_types(stackable_values)
+        variant_types = {}
+        return variant_types unless defined?(Grape::Validations::Types::VariantCollectionCoercer) &&
+                                    defined?(Grape::Validations::Validators::CoerceValidator) &&
+                                    stackable_values.respond_to?(:[])
+
+        Array(stackable_values[:validations]).each do |validator|
+          next unless validator.is_a?(Grape::Validations::Validators::CoerceValidator)
+
+          converter = validator.instance_variable_get(:@converter)
+          next unless converter.is_a?(Grape::Validations::Types::VariantCollectionCoercer)
+
+          types = converter.instance_variable_get(:@types)
+          Array(validator.instance_variable_get(:@attrs)).each do |attr|
+            variant_types[attr.to_s] = types
+          end
+        end
+
+        variant_types
+      end
+
+      def fulfill_params(path_params, variant_types)
         # Merge path params options into route params
         route.params.each_with_object({}) do |(param, definition), accum|
           # The route.params hash includes both parametrized params (with a string as a key)
@@ -57,10 +84,18 @@ def fulfill_params(path_params)
           next if param.is_a?(String) && accum.key?(key)
 
           defined_options = definition.is_a?(Hash) ? definition : {}
+          defined_options = restore_variant_type(defined_options, param, variant_types)
           value = (path_params[param] || {}).merge(defined_options)
           accum[key] = value.empty? ? DEFAULT_PARAM_TYPE : value
         end
       end
+
+      def restore_variant_type(defined_options, param, variant_types)
+        types = variant_types[param.to_s]
+        return defined_options unless types
+
+        defined_options.merge(type: types)
+      end
     end
   end
 end
diff --git a/spec/support/model_parsers/mock_parser.rb b/spec/support/model_parsers/mock_parser.rb
index 13bdcc04c..de6d24c00 100644
--- a/spec/support/model_parsers/mock_parser.rb
+++ b/spec/support/model_parsers/mock_parser.rb
@@ -72,7 +72,13 @@ class RecursiveModel < OpenStruct; end
       class DocumentedHashAndArrayModel < OpenStruct; end
 
       module NestedModule
-        class ApiResponse < OpenStruct; end
+        class ApiResponse < OpenStruct
+          # Grape 3.2+ requires unknown types to implement .parse (arity 1) to pass the
+          # Types.custom? check and avoid a dry-types lookup that would raise ArgumentError.
+          # The implementation is minimal because these tests exercise swagger doc generation
+          # only, not actual request coercion.
+          def self.parse(val) = val
+        end
       end
     end
   end
diff --git a/spec/support/model_parsers/representable_parser.rb b/spec/support/model_parsers/representable_parser.rb
index 2102ce8aa..d56fbd4de 100644
--- a/spec/support/model_parsers/representable_parser.rb
+++ b/spec/support/model_parsers/representable_parser.rb
@@ -99,6 +99,11 @@ class ApiResponse < Representable::Decorator
 
           property :status, documentation: { type: String }
           property :error, documentation: { type: ::Entities::ApiError }
+
+          # Grape 3.2+ requires unknown types to implement .parse (arity 1) to pass the
+          # Types.custom? check. Representable::Decorator does not define parse, so we add
+          # a minimal pass-through sufficient for documentation-generation tests.
+          def self.parse(val) = val
         end
       end
 
diff --git a/spec/swagger_v2/params_example_spec.rb b/spec/swagger_v2/params_example_spec.rb
index fbddf7cca..f3504e03d 100644
--- a/spec/swagger_v2/params_example_spec.rb
+++ b/spec/swagger_v2/params_example_spec.rb
@@ -11,7 +11,10 @@ def app
         params :common_params do
           requires :id, type: Integer, documentation: { example: 123 }
           optional :name, type: String, documentation: { example: 'Person' }
-          optional :obj, type: 'Object', documentation: { example: { 'foo' => 'bar' } }
+          # 'Object' is not a valid Grape coercion type; it is a swagger documentation-only hint.
+          # Grape 3.2+ rejects string type names in params blocks, so the type lives in
+          # documentation: where grape-swagger picks it up via ParseParams#call settings merge.
+          optional :obj, documentation: { type: 'Object', example: { 'foo' => 'bar' } }
         end
       end