diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ab70543fa..803afd64c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -44,6 +44,25 @@ jobs:
       - name: Test
         run: bundle exec rake smithy:spec
 
+  smithy-rbs:
+    needs: [smithy]
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ env.latest_ruby_version }}
+          bundler-cache: true
+
+      - name: Install rbs collection
+        run: rbs collection install
+
+      - name: RBS
+        run: bundle exec rake smithy:rbs
+
   smithy-schema:
     uses: ./.github/workflows/test.yml
     with:
diff --git a/gems/smithy-client/lib/smithy-client.rb b/gems/smithy-client/lib/smithy-client.rb
index 00156cec6..42149983f 100644
--- a/gems/smithy-client/lib/smithy-client.rb
+++ b/gems/smithy-client/lib/smithy-client.rb
@@ -51,6 +51,7 @@
 # identity and auth
 
 require_relative 'smithy-client/auth'
+require_relative 'smithy-client/auth_option'
 require_relative 'smithy-client/auth_scheme'
 require_relative 'smithy-client/identity_provider'
 require_relative 'smithy-client/null_signer'
diff --git a/gems/smithy-client/lib/smithy-client/api_key_signer.rb b/gems/smithy-client/lib/smithy-client/api_key_signer.rb
index 7da952c26..0526c3d7f 100644
--- a/gems/smithy-client/lib/smithy-client/api_key_signer.rb
+++ b/gems/smithy-client/lib/smithy-client/api_key_signer.rb
@@ -4,6 +4,13 @@ module Smithy
   module Client
     # Signs requests with the ApiKey identity.
     class ApiKeySigner
+      # @param [Hash] options
+      # @option options [String] :name
+      #   The name of the header or query parameter to which the API key value will be assigned.
+      # @option options [String] :in
+      #   Where to place the API key value. Valid values are "header" and "query".
+      # @option options [String] :scheme
+      #   An optional scheme to be prepended to the API key value when signing in a header.
       def initialize(options = {})
         @name = options[:name]
         @in = options[:in]
diff --git a/gems/smithy-client/lib/smithy-client/auth.rb b/gems/smithy-client/lib/smithy-client/auth.rb
index 87d56a20e..df6547b86 100644
--- a/gems/smithy-client/lib/smithy-client/auth.rb
+++ b/gems/smithy-client/lib/smithy-client/auth.rb
@@ -32,7 +32,10 @@ def resolve_with_endpoint_auth(config, endpoint_auth_schemes)
 
               properties[key] = value
             end
-            normalized_endpoint_schemes << { scheme_id: normalized_scheme_id, signer_properties: properties }
+            normalized_endpoint_schemes << AuthOption.new(
+              scheme_id: normalized_scheme_id,
+              signer_properties: properties
+            )
           end
           resolved_auth_options = prioritize_auth_options(normalized_endpoint_schemes, config.auth_scheme_preference)
           resolve_auth_scheme(config.auth_schemes, resolved_auth_options)
@@ -49,7 +52,7 @@ def prioritize_auth_options(auth_options, auth_scheme_preference)
 
           auth_options_by_id = {}
           auth_options.each do |option|
-            auth_options_by_id[option[:scheme_id]] = option
+            auth_options_by_id[option.scheme_id] = option
           end
 
           preferred_options = []
@@ -63,25 +66,22 @@ def prioritize_auth_options(auth_options, auth_scheme_preference)
           preferred_options.empty? ? auth_options : preferred_options
         end
 
-        def resolve_auth_scheme(auth_schemes, auth_options) # rubocop:disable Metrics/MethodLength
+        def resolve_auth_scheme(auth_schemes, auth_options)
           raise 'No auth options were resolved' if auth_options.empty?
 
           failures = []
           auth_options.each do |auth_option|
-            scheme_id = auth_option[:scheme_id]
-            if scheme_id == 'smithy.api#noAuth'
-              return ResolvedAuth.new(
-                scheme_id: 'smithy.api#noAuth', signer: NullSigner.new, signer_properties: {},
-                identity_provider: nil
-              )
-            end
+            scheme_id = auth_option.scheme_id
+            return ResolvedAuth.new(scheme_id: scheme_id, signer: NullSigner.new) if scheme_id == 'smithy.api#noAuth'
+
             auth_scheme = auth_schemes[scheme_id]
             error = validate_auth_scheme(auth_scheme, scheme_id)
+
             unless error
               return ResolvedAuth.new(
                 scheme_id: scheme_id,
                 signer: auth_scheme.signer,
-                signer_properties: auth_option[:signer_properties] || {},
+                signer_properties: auth_option.signer_properties,
                 identity_provider: auth_scheme.identity_provider
               )
             end
diff --git a/gems/smithy-client/lib/smithy-client/auth_option.rb b/gems/smithy-client/lib/smithy-client/auth_option.rb
new file mode 100644
index 000000000..87206fc43
--- /dev/null
+++ b/gems/smithy-client/lib/smithy-client/auth_option.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Smithy
+  module Client
+    # Contains information about candidate authentication schemes.
+    class AuthOption
+      # @param [Hash] options
+      # @option options [String] :scheme_id The auth scheme ID.
+      # @option options [Hash] :signer_properties
+      #   Additional properties to pass to the signer.
+      #   This is a hash of String keys to String values and is signer-specific.
+      def initialize(options = {})
+        @scheme_id = options[:scheme_id]
+        @signer_properties = options[:signer_properties] || {}
+      end
+
+      # @return [String]
+      attr_reader :scheme_id
+
+      # @return [Hash]
+      attr_reader :signer_properties
+    end
+  end
+end
diff --git a/gems/smithy-client/lib/smithy-client/login_signer.rb b/gems/smithy-client/lib/smithy-client/login_signer.rb
index 4f6e5754a..441d4e84b 100644
--- a/gems/smithy-client/lib/smithy-client/login_signer.rb
+++ b/gems/smithy-client/lib/smithy-client/login_signer.rb
@@ -4,12 +4,15 @@ module Smithy
   module Client
     # Signs requests with the Login identity.
     class LoginSigner
+      # @param [Hash] options
+      # @option options [Symbol] :type
+      #  The type of login authentication. Valid values are: :http_basic.
       def initialize(options = {})
-        @scheme_id = options[:scheme_id]
+        @type = options[:type]
       end
 
       def sign_request(context)
-        raise NotImplementedError unless @scheme_id == 'smithy.api#httpBasicAuth'
+        raise NotImplementedError unless @type == :http_basic
 
         sign_with_basic(context.http_request, context.config.login_provider)
       end
diff --git a/gems/smithy-client/lib/smithy-client/plugins/http_api_key_auth.rb b/gems/smithy-client/lib/smithy-client/plugins/http_api_key_auth.rb
index 5da78610b..365539dbc 100644
--- a/gems/smithy-client/lib/smithy-client/plugins/http_api_key_auth.rb
+++ b/gems/smithy-client/lib/smithy-client/plugins/http_api_key_auth.rb
@@ -28,7 +28,11 @@ class that responds to #identity and returns a {Smithy::Client::ApiKey}.
           provider if provider.set?
         end
 
-        option(:api_key_signer) do |config|
+        option(
+          :api_key_signer,
+          doc_type: Smithy::Client::ApiKeySigner,
+          docstring: 'A signer class that signs requests with an API key.'
+        ) do |config|
           trait = config.service.traits['smithy.api#httpApiKeyAuth']
           ApiKeySigner.new(name: trait['name'], in: trait['in'], scheme: trait['scheme'])
         end
diff --git a/gems/smithy-client/lib/smithy-client/plugins/http_basic_auth.rb b/gems/smithy-client/lib/smithy-client/plugins/http_basic_auth.rb
index c16df797f..34b61e652 100644
--- a/gems/smithy-client/lib/smithy-client/plugins/http_basic_auth.rb
+++ b/gems/smithy-client/lib/smithy-client/plugins/http_basic_auth.rb
@@ -36,8 +36,12 @@ class that responds to #identity and returns a {Smithy::Client::Login}.
           provider if provider.set?
         end
 
-        option(:login_signer) do |_config|
-          LoginSigner.new(scheme_id: 'smithy.api#httpBasicAuth')
+        option(
+          :login_signer,
+          doc_type: Smithy::Client::LoginSigner,
+          docstring: 'A signer class that signs requests with login credentials.'
+        ) do |_config|
+          LoginSigner.new(type: :http_basic)
         end
 
         def after_initialize(client)
diff --git a/gems/smithy-client/lib/smithy-client/plugins/http_bearer_auth.rb b/gems/smithy-client/lib/smithy-client/plugins/http_bearer_auth.rb
index 0c48363df..21710cbd1 100644
--- a/gems/smithy-client/lib/smithy-client/plugins/http_bearer_auth.rb
+++ b/gems/smithy-client/lib/smithy-client/plugins/http_bearer_auth.rb
@@ -28,7 +28,11 @@ class that responds to #identity and returns a {Smithy::Client::BearerToken}.
           provider if provider.set?
         end
 
-        option(:bearer_token_signer) do |_config|
+        option(
+          :bearer_token_signer,
+          doc_type: Smithy::Client::BearerTokenSigner,
+          docstring: 'A signer class that signs requests with a bearer token.'
+        ) do |_config|
           BearerTokenSigner.new
         end
 
diff --git a/gems/smithy-client/lib/smithy-client/plugins/http_digest_auth.rb b/gems/smithy-client/lib/smithy-client/plugins/http_digest_auth.rb
index a6743a4fb..314af415b 100644
--- a/gems/smithy-client/lib/smithy-client/plugins/http_digest_auth.rb
+++ b/gems/smithy-client/lib/smithy-client/plugins/http_digest_auth.rb
@@ -36,8 +36,12 @@ class that responds to #identity and returns a {Smithy::Client::Login}.
           provider if provider.set?
         end
 
-        option(:login_signer) do |_config|
-          LoginSigner.new(scheme_id: 'smithy.api#httpDigestAuth')
+        option(
+          :login_signer,
+          doc_type: Smithy::Client::LoginSigner,
+          docstring: 'A signer class that signs requests with login credentials.'
+        ) do |_config|
+          LoginSigner.new(type: :http_digest)
         end
 
         def after_initialize(client)
diff --git a/gems/smithy-client/sig/smithy-client/auth_option.rbs b/gems/smithy-client/sig/smithy-client/auth_option.rbs
new file mode 100644
index 000000000..235c1f87f
--- /dev/null
+++ b/gems/smithy-client/sig/smithy-client/auth_option.rbs
@@ -0,0 +1,9 @@
+module Smithy
+  module Client
+    module AuthOption
+      def initialize: (?Hash[Symbol, untyped] options) -> void
+      attr_reader scheme_id: String
+      attr_reader signer_properties: Hash[String, String] 
+    end
+  end
+end
diff --git a/gems/smithy-client/sig/smithy-client/service_error.rbs b/gems/smithy-client/sig/smithy-client/service_error.rbs
index 68873e9e7..3a67288e8 100644
--- a/gems/smithy-client/sig/smithy-client/service_error.rbs
+++ b/gems/smithy-client/sig/smithy-client/service_error.rbs
@@ -1,11 +1,11 @@
 module Smithy
   module Client
     class ServiceError < RuntimeError
-      def initialize: (HandlerContext, Schema::Structure) -> void
+      def initialize: (HandlerContext?, Schema::Structure?) -> void
 
       attr_reader code: String?
-      attr_reader context: HandlerContext
-      attr_accessor data: untyped?
+      attr_reader context: HandlerContext?
+      attr_accessor data: Schema::Structure?
 
       def self.code: () -> String?
       def self.code=: (String) -> void
diff --git a/gems/smithy-client/spec/smithy-client/plugins/resolve_auth_spec.rb b/gems/smithy-client/spec/smithy-client/plugins/resolve_auth_spec.rb
index 6bb86ee8d..828fb0917 100644
--- a/gems/smithy-client/spec/smithy-client/plugins/resolve_auth_spec.rb
+++ b/gems/smithy-client/spec/smithy-client/plugins/resolve_auth_spec.rb
@@ -107,10 +107,10 @@ module Plugins
           auth_resolver = Class.new do
             def resolve(_)
               [
-                {
+                AuthOption.new(
                   scheme_id: 'smithy.api#httpApiKeyAuth',
                   signer_properties: { 'location' => 'query', 'name' => 'api_key' }
-                }
+                )
               ]
             end
           end
diff --git a/gems/smithy/lib/smithy/templates/client/auth_resolver.erb b/gems/smithy/lib/smithy/templates/client/auth_resolver.erb
index a106f57d0..3ac833c77 100644
--- a/gems/smithy/lib/smithy/templates/client/auth_resolver.erb
+++ b/gems/smithy/lib/smithy/templates/client/auth_resolver.erb
@@ -6,7 +6,7 @@ module <%= module_name %>
   # Resolves the auth scheme from {AuthParameters}.
   class AuthResolver
     # @param [AuthParameters] parameters
-    # @return [Array<Hash>]
+    # @return [Array<Smithy::Client::AuthOption>]
     def resolve(parameters)
 <% auth_rules_code.each do |line| -%>
       <%= line %>
diff --git a/gems/smithy/lib/smithy/templates/client/auth_resolver_rbs.erb b/gems/smithy/lib/smithy/templates/client/auth_resolver_rbs.erb
index 317925dd6..b615ea66f 100644
--- a/gems/smithy/lib/smithy/templates/client/auth_resolver_rbs.erb
+++ b/gems/smithy/lib/smithy/templates/client/auth_resolver_rbs.erb
@@ -1,5 +1,5 @@
 module <%= module_name %>
   class AuthResolver
-    def resolve: (AuthParameters) -> Array[String]
+    def resolve: (AuthParameters) -> Array[Smithy::Client::AuthOption]
   end
 end
diff --git a/gems/smithy/lib/smithy/views/client/auth_resolver.rb b/gems/smithy/lib/smithy/views/client/auth_resolver.rb
index bad2a78a0..c95f83b11 100644
--- a/gems/smithy/lib/smithy/views/client/auth_resolver.rb
+++ b/gems/smithy/lib/smithy/views/client/auth_resolver.rb
@@ -35,7 +35,7 @@ def auth_rules_code
 
         def add_service_auth_schemes_to_code(lines)
           service_auth_schemes.each do |auth_scheme|
-            lines << "options << { scheme_id: '#{auth_scheme}' }"
+            lines << "options << Smithy::Client::AuthOption.new(scheme_id: '#{auth_scheme}')"
           end
         end
 
@@ -53,7 +53,7 @@ def add_operation_case_to_code(lines, auth_operations)
 
         def add_operation_auth_options_to_code(lines, operation)
           operation_auth_schemes(operation).each do |auth_scheme|
-            lines << "  options << { scheme_id: '#{auth_scheme}' }"
+            lines << "  options << Smithy::Client::AuthOption.new(scheme_id: '#{auth_scheme}')"
           end
         end
 
diff --git a/gems/smithy/spec/interfaces/client/auth_resolver_spec.rb b/gems/smithy/spec/interfaces/client/auth_resolver_spec.rb
index 0c4177751..ef778da7f 100644
--- a/gems/smithy/spec/interfaces/client/auth_resolver_spec.rb
+++ b/gems/smithy/spec/interfaces/client/auth_resolver_spec.rb
@@ -16,30 +16,30 @@
           params = NoAuthTrait::AuthParameters.new(operation_name: :operation_a)
           auth_options = subject.resolve(params)
           expected = [
-            { scheme_id: 'smithy.api#httpBasicAuth' },
-            { scheme_id: 'smithy.api#httpBearerAuth' },
-            { scheme_id: 'smithy.api#httpDigestAuth' }
+            'smithy.api#httpBasicAuth',
+            'smithy.api#httpBearerAuth',
+            'smithy.api#httpDigestAuth'
           ]
-          expect(auth_options).to eq(expected)
+          expect(auth_options.map(&:scheme_id)).to eq(expected)
         end
 
         it 'returns the auth options for the operation with the auth trait' do
           params = NoAuthTrait::AuthParameters.new(operation_name: :operation_b)
           auth_options = subject.resolve(params)
-          expect(auth_options).to eq([{ scheme_id: 'smithy.api#httpDigestAuth' }])
+          expected = ['smithy.api#httpDigestAuth']
+          expect(auth_options.map(&:scheme_id)).to eq(expected)
         end
 
         it 'returns the auth options for the operation with the optionalAuth trait' do
           params = NoAuthTrait::AuthParameters.new(operation_name: :operation_g)
           auth_options = subject.resolve(params)
-          expect(auth_options).to eq(
-            [
-              { scheme_id: 'smithy.api#httpBasicAuth' },
-              { scheme_id: 'smithy.api#httpBearerAuth' },
-              { scheme_id: 'smithy.api#httpDigestAuth' },
-              { scheme_id: 'smithy.api#noAuth' }
-            ]
-          )
+          expected = [
+            'smithy.api#httpBasicAuth',
+            'smithy.api#httpBearerAuth',
+            'smithy.api#httpDigestAuth',
+            'smithy.api#noAuth'
+          ]
+          expect(auth_options.map(&:scheme_id)).to eq(expected)
         end
       end
     end
@@ -53,32 +53,33 @@
         it 'returns the auth options with the service auth trait' do
           params = AuthTrait::AuthParameters.new(operation_name: :operation_c)
           auth_options = subject.resolve(params)
-          expected = [{ scheme_id: 'smithy.api#httpBasicAuth' }, { scheme_id: 'smithy.api#httpDigestAuth' }]
-          expect(auth_options).to eq(expected)
+          expected = ['smithy.api#httpBasicAuth', 'smithy.api#httpDigestAuth']
+          expect(auth_options.map(&:scheme_id)).to eq(expected)
         end
 
         it 'returns the auth options for the operation overriding the service auth trait' do
           params = AuthTrait::AuthParameters.new(operation_name: :operation_d)
           auth_options = subject.resolve(params)
-          expect(auth_options).to eq([{ scheme_id: 'smithy.api#httpBearerAuth' }])
+          expected = ['smithy.api#httpBearerAuth']
+          expect(auth_options.map(&:scheme_id)).to eq(expected)
         end
 
         it 'returns a noAuth option when the auth trait is empty' do
           params = AuthTrait::AuthParameters.new(operation_name: :operation_e)
           auth_options = subject.resolve(params)
-          expect(auth_options).to eq([{ scheme_id: 'smithy.api#noAuth' }])
+          expected = ['smithy.api#noAuth']
+          expect(auth_options.map(&:scheme_id)).to eq(expected)
         end
 
         it 'returns the auth options for the operation with the optionalAuth trait' do
           params = AuthTrait::AuthParameters.new(operation_name: :operation_f)
           auth_options = subject.resolve(params)
-          expect(auth_options).to eq(
-            [
-              { scheme_id: 'smithy.api#httpBasicAuth' },
-              { scheme_id: 'smithy.api#httpDigestAuth' },
-              { scheme_id: 'smithy.api#noAuth' }
-            ]
-          )
+          expected = [
+            'smithy.api#httpBasicAuth',
+            'smithy.api#httpDigestAuth',
+            'smithy.api#noAuth'
+          ]
+          expect(auth_options.map(&:scheme_id)).to eq(expected)
         end
       end
     end
@@ -92,13 +93,15 @@
         it 'returns the auth options for the operation with no auth traits' do
           params = NoAuth::AuthParameters.new(operation_name: :operation_h)
           auth_options = subject.resolve(params)
-          expect(auth_options).to eq([{ scheme_id: 'smithy.api#noAuth' }])
+          expected = ['smithy.api#noAuth']
+          expect(auth_options.map(&:scheme_id)).to eq(expected)
         end
 
         it 'returns the auth options for the operation with the optionalAuth trait' do
           params = NoAuth::AuthParameters.new(operation_name: :operation_i)
           auth_options = subject.resolve(params)
-          expect(auth_options).to eq([{ scheme_id: 'smithy.api#noAuth' }])
+          expected = ['smithy.api#noAuth']
+          expect(auth_options.map(&:scheme_id)).to eq(expected)
         end
       end
     end
diff --git a/gems/smithy/spec/interfaces/welds/auth_schemes_spec.rb b/gems/smithy/spec/interfaces/welds/auth_schemes_spec.rb
index 46a343832..aa2be542f 100644
--- a/gems/smithy/spec/interfaces/welds/auth_schemes_spec.rb
+++ b/gems/smithy/spec/interfaces/welds/auth_schemes_spec.rb
@@ -36,14 +36,14 @@ def remove_auth_schemes
         auth_resolver = ServiceWithAuthTrait::AuthResolver.new
         auth_parameters = ServiceWithAuthTrait::AuthParameters.new(operation_name: :operation_c)
         resolved_auths = auth_resolver.resolve(auth_parameters)
-        expect(resolved_auths).to include({ scheme_id: 'smithy.api#httpBasicAuth' })
+        expect(resolved_auths.map(&:scheme_id)).to include('smithy.api#httpBasicAuth')
       end
 
       it 'removes auth schemes from the client' do
         auth_resolver = ServiceWithAuthTrait::AuthResolver.new
         auth_parameters = ServiceWithAuthTrait::AuthParameters.new(operation_name: :operation_d)
         resolved_auths = auth_resolver.resolve(auth_parameters)
-        expect(resolved_auths).to_not include({ scheme_id: 'smithy.api#httpBearerAuth' })
+        expect(resolved_auths.map(&:scheme_id)).to_not include('smithy.api#httpBearerAuth')
       end
     end
   end