diff --git a/docs/src/SUMMARY.md b/docs/src/SUMMARY.md
index bed30d12..57ee195e 100644
--- a/docs/src/SUMMARY.md
+++ b/docs/src/SUMMARY.md
@@ -81,6 +81,7 @@
   - [Multiple callbacks](callbacks/multiple-callbacks.md)
   - [Global callbacks](callbacks/global-callbacks.md)
   - [Symbol#to_proc](callbacks/symbol-to_proc.md)
+  - [Callback parameters](callbacks/callback-parameters.md)
 - [Modifying factories](modifying-factories/summary.md)
 - [Linting Factories](linting-factories/summary.md)
 - [Custom Construction](custom-construction/summary.md)
diff --git a/docs/src/callbacks/callback-parameters.md b/docs/src/callbacks/callback-parameters.md
new file mode 100644
index 00000000..50f40b86
--- /dev/null
+++ b/docs/src/callbacks/callback-parameters.md
@@ -0,0 +1,112 @@
+# Callback parameters
+
+Callbacks can receive zero, one or two parameters.
+
+## With zero parameters
+
+Callbacks with zero parameters simply execute the provided block of code:
+```ruby
+factory :user do
+  after(:stub)   { do_something() }
+end
+```
+
+## With one parameter
+
+Callbacks with a single parameter receive the factory instance being constructed:
+```ruby
+factory :user do
+  after(:build)  { |user| do_something_to(user) }
+end
+```
+
+## With two parameters
+
+Callbacks with two parameters receive both the factory instance 
+and the context in which the instance is constructed:
+```ruby
+factory :user do
+  transient { article { <article> } }
+
+  after(:create) { |user, context| user.post_first_article(context.article) }
+end
+```
+
+## Callback context
+
+The `context` parameter provides access to the environment in which the 
+instance is constructed.
+
+### Transient settings
+
+Transient settings are accessed directly from the `context`:
+```ruby
+factory :car do
+  transient { doors { 4 } }
+
+  after(:create) do |car, context| 
+    car.update(style: :sedan) if context.doors == 4 
+    car.update(style: :coupe) if context.doors == 2
+  end 
+end
+
+car = FactoryBot.create(:car, doors: 2)
+car.style #=> :coupe
+```
+
+### Strategy used
+
+Sometimes you have a factory that you both `build` and `create` in different tests,
+but always want the same code to run at the end. 
+
+It's not as simple as adding both `after(:build)` and `after(:create)` callbacks because `after(:create)` also triggers the `after(:build)` callback, so the code would be run twice.
+
+Checking for the strategy used can help skip the `after(:build)` code when the strategy used is `create`.
+```ruby
+factory :user do
+  after(:build) { |user, context| run_this_code() if context.strategy.build?}
+  after(:create) { |user, context| run_this_code() }
+end
+```
+
+### Defined attributes
+Sometimes you need to know if an attribute was provided by the user or defined by the factory. `context` provides a list of the attributes which have been defined: in total; by the user; or by the factory. The list may also be queried for a simgle entry:
+```ruby
+# based on FactoryBot.build(:car, doors: 2)
+factory :car do
+  transient { transmission { :manual } }
+
+  doors  { 4 }
+  seats  { 5 }
+  wheels { 6 }
+
+  after(:build) do |car, context| 
+    context.defined_attributes                 #=> [:doors, :seats, :wheels]
+    context.user_defined_attributes            #=> [:doors]
+    context.factory_defined_attributes         #=> [:seats, :wheels]
+
+    context.defined_attributes.wheels?         #=> true
+    context.user_defined_attributes.wheels?    #=> false
+    context.factory_defined_attributes.wheels? #=> true
+  end 
+end
+```
+
+**Note**: Transient attributes are not included in the list unless they have been provided
+by the user.
+```ruby
+# based on FactoryBot.build(:car, doors: 2, transmission: :automatic)
+factory :car do
+  transient { transmission { :manual } }
+
+  doors  { 4 }
+  seats  { 5 }
+  wheels { 6 }
+
+  after(:build) do |car, context| 
+    context.defined_attributes         #=> [:doors, :seats, :transmission :wheels]
+    context.user_defined_attributes    #=> [:doors, :transmission]
+    context.factory_defined_attributes #=> [:seats, :wheels]
+  end 
+end
+```
\ No newline at end of file
diff --git a/lib/factory_bot.rb b/lib/factory_bot.rb
index b5c75145..bde70bed 100644
--- a/lib/factory_bot.rb
+++ b/lib/factory_bot.rb
@@ -46,6 +46,7 @@
 require "factory_bot/decorator/disallows_duplicates_registry"
 require "factory_bot/decorator/invocation_tracker"
 require "factory_bot/decorator/new_constructor"
+require "factory_bot/inquiry"
 require "factory_bot/linter"
 require "factory_bot/version"
 
diff --git a/lib/factory_bot/evaluator.rb b/lib/factory_bot/evaluator.rb
index 7a4b82e7..a8c84b31 100644
--- a/lib/factory_bot/evaluator.rb
+++ b/lib/factory_bot/evaluator.rb
@@ -13,6 +13,7 @@ class Evaluator
     def initialize(build_strategy, overrides = {})
       @build_strategy = build_strategy
       @overrides = overrides
+      @user_overrides = overrides.keys
       @cached_attributes = overrides
       @instance = nil
 
@@ -35,6 +36,24 @@ def association(factory_name, *traits_and_overrides)
 
     attr_accessor :instance
 
+    def strategy
+      @build_strategy.to_sym.to_s.extend(FactoryBot::Inquiry)
+    rescue NoMethodError # for custom strategies without :to_sym
+      "unknown".extend(FactoryBot::Inquiry)
+    end
+
+    def defined_attributes
+      __override_names__.sort.extend(FactoryBot::Inquiry)
+    end
+
+    def user_defined_attributes
+      @user_overrides.sort.extend(FactoryBot::Inquiry)
+    end
+
+    def factory_defined_attributes
+      (__override_names__ - @user_overrides).sort.extend(FactoryBot::Inquiry)
+    end
+
     def method_missing(method_name, ...)
       if @instance.respond_to?(method_name)
         @instance.send(method_name, ...)
diff --git a/lib/factory_bot/inquiry.rb b/lib/factory_bot/inquiry.rb
new file mode 100644
index 00000000..022d7a7a
--- /dev/null
+++ b/lib/factory_bot/inquiry.rb
@@ -0,0 +1,26 @@
+module FactoryBot
+  module Inquiry
+    def respond_to_missing?(name, include_private = false)
+      name.end_with?("?") || super
+    end
+
+    def method_missing(name, ...)
+      if name.end_with?("?")
+        fb_inquire(name[0..-2])
+      else
+        super
+      end
+    end
+
+    def fb_inquire(test_value)
+      case self
+      when String
+        self == test_value
+      when Array
+        include?(test_value) || include?(test_value.to_sym)
+      else
+        false
+      end
+    end
+  end
+end
diff --git a/spec/factory_bot/evaluator/provided_attributes_spec.rb b/spec/factory_bot/evaluator/provided_attributes_spec.rb
new file mode 100644
index 00000000..5ab67d99
--- /dev/null
+++ b/spec/factory_bot/evaluator/provided_attributes_spec.rb
@@ -0,0 +1,58 @@
+describe FactoryBot::Evaluator do
+  context :methods do
+    before(:all) {
+      unless defined?(ContextAttributeTest)
+        class ContextAttributeTest
+          attr_accessor :name, :age, :admin, :results
+
+          def initialize
+            self.results = {}
+          end
+        end
+      end
+    }
+
+    after(:all) {
+      if defined?(ContextAttributeTest)
+        Object.send(:remove_const, :ContextAttributeTest)
+      end
+    }
+
+    before(:each) {
+      FactoryBot.define do
+        factory :context_attribute_test do
+          transient do
+            trans_attr { false }
+          end
+
+          name { "John Doh" }
+          age { 23 }
+          admin { false }
+
+          after(:build) do |object, context|
+            object.results[:defined_attributes] = context.defined_attributes
+            object.results[:user_defined_attributes] = context.user_defined_attributes
+            object.results[:factory_defined_attributes] = context.factory_defined_attributes
+          end
+        end
+      end
+    }
+
+    context ":defined_attributes" do
+      it "lists all provided attributes" do
+        obj = FactoryBot.build :context_attribute_test, admin: true, trans_attr: true
+        expect(obj.results[:defined_attributes]).to eq [:admin, :age, :name, :trans_attr]
+      end
+
+      it "lists the user provided attributes" do
+        obj = FactoryBot.build :context_attribute_test, admin: true, trans_attr: true
+        expect(obj.results[:user_defined_attributes]).to eq [:admin, :trans_attr]
+      end
+
+      it "lists the factory provided attributes" do
+        obj = FactoryBot.build :context_attribute_test, admin: true, trans_attr: true
+        expect(obj.results[:factory_defined_attributes]).to eq [:age, :name]
+      end
+    end
+  end
+end
diff --git a/spec/factory_bot/evaluator/strategy_used_spec.rb b/spec/factory_bot/evaluator/strategy_used_spec.rb
new file mode 100644
index 00000000..30377263
--- /dev/null
+++ b/spec/factory_bot/evaluator/strategy_used_spec.rb
@@ -0,0 +1,111 @@
+describe FactoryBot::Evaluator do
+  context :methods do
+    context ":stragtegy" do
+      context "on success" do
+        context "with FactoryBot::Strategy::Null" do
+          let(:evaluator) { define_evaluator(FactoryBot::Strategy::Null) }
+
+          it "returns the string 'null'" do
+            expect(evaluator.strategy).to eq "null"
+          end
+
+          it "returns true with the correct inquiry :null?" do
+            expect(evaluator.strategy).to be_null
+          end
+
+          it "returns false with the incorrect inquiry :build?" do
+            expect(evaluator.strategy).not_to be_build
+          end
+        end
+
+        context "with FactoryBot::Strategy::Build" do
+          let(:evaluator) { define_evaluator(FactoryBot::Strategy::Build) }
+
+          it "returns the string 'build'" do
+            expect(evaluator.strategy).to eq "build"
+          end
+
+          it "returns true with the correct inquiry :build?" do
+            expect(evaluator.strategy).to be_build
+          end
+
+          it "returns false with an incorrect inquiry :create" do
+            expect(evaluator.strategy).not_to be_create
+          end
+        end
+
+        context "with FactoryBot::Strategy::Stub" do
+          let(:evaluator) { define_evaluator(FactoryBot::Strategy::Stub) }
+
+          it "returns the string 'stub'" do
+            expect(evaluator.strategy).to eq "stub"
+          end
+
+          it "returns true with the correct inquiry :stub?" do
+            expect(evaluator.strategy).to be_stub
+          end
+
+          it "returns false with the incorrect inquiry :build?" do
+            expect(evaluator.strategy).not_to be_build
+          end
+        end
+
+        context "with FactoryBot::Strategy::Create" do
+          let(:evaluator) { define_evaluator(FactoryBot::Strategy::Create) }
+
+          it "returns the string 'create'" do
+            expect(evaluator.strategy).to eq "create"
+          end
+
+          it "returns true with the correct inquiry :create?" do
+            expect(evaluator.strategy).to be_create
+          end
+
+          it "returns false with the incorrect inquiry :build?" do
+            expect(evaluator.strategy).not_to be_build
+          end
+        end
+
+        context "with FactoryBot::Strategy::AttributesFor" do
+          let(:evaluator) { define_evaluator(FactoryBot::Strategy::AttributesFor) }
+
+          it "returns the string 'attributes_for'" do
+            expect(evaluator.strategy).to eq "attributes_for"
+          end
+
+          it "returns true with the correct inquiry :attributes_for?" do
+            expect(evaluator.strategy).to be_attributes_for
+          end
+
+          it "returns false with the incorrect inquiry :build?" do
+            expect(evaluator.strategy).not_to be_build
+          end
+        end
+      end # on success
+
+      context "on failure" do
+        let(:evaluator) do
+          strategy = FactoryBot::Strategy::Null.new
+          allow(strategy).to receive(:to_sym).and_raise(NoMethodError)
+          FactoryBot::Evaluator.new(strategy)
+        end
+
+        it "returns 'unknown' when strategy does not implement :to_sym" do
+          expect(evaluator.strategy).to eq "unknown"
+        end
+
+        it "returns true with the correct inquiry :unknown?" do
+          expect(evaluator.strategy).to be_unknown
+        end
+
+        it "returns false with the incorrect inquiry :build?" do
+          expect(evaluator.strategy).not_to be_build
+        end
+      end # on failure
+    end
+  end
+
+  def define_evaluator(build_strategy = FactoryBot::Strategy::Null)
+    FactoryBot::Evaluator.new(build_strategy.new)
+  end
+end
diff --git a/spec/factory_bot/inquiry_spec.rb b/spec/factory_bot/inquiry_spec.rb
new file mode 100644
index 00000000..fc683142
--- /dev/null
+++ b/spec/factory_bot/inquiry_spec.rb
@@ -0,0 +1,42 @@
+describe FactoryBot::Inquiry do
+  context "extends a String with inquiry methods" do
+    let(:str) { "test".extend(FactoryBot::Inquiry) }
+
+    it "returns true with a valid inquiry" do
+      expect(str).to be_test
+    end
+
+    it "returns false with an invalid inquiry" do
+      expect(str).not_to be_good
+    end
+
+    it "ignores an inquiry that dosen't end with '?'" do
+      expect { str.bad }.to raise_error NoMethodError
+    end
+  end
+
+  context "extends an Array with inquiry methods" do
+    let(:ary) { ["test", :fact, "Bot"].extend(FactoryBot::Inquiry) }
+
+    it "return true if the array includes a string version of the inquiry" do
+      expect(ary).to be_test
+    end
+
+    it "return true if the array includes a symbol version of the inquiry" do
+      expect(ary).to be_fact
+    end
+
+    it "returns false if the array does not include the inquiry" do
+      expect(ary).not_to be_good
+    end
+
+    it "ignores an inquiry that dosen't end with '?'" do
+      expect { ary.bad }.to raise_error NoMethodError
+    end
+  end
+
+  it "always returns false with a non-String or non-Array object" do
+    obj = Time.now.extend(FactoryBot::Inquiry)
+    expect(obj).not_to be_time?
+  end
+end