diff --git a/lib/telebugs.rb b/lib/telebugs.rb
index eb002ae..e85b038 100644
--- a/lib/telebugs.rb
+++ b/lib/telebugs.rb
@@ -1,24 +1,30 @@
 # frozen_string_literal: true
 
 require "concurrent"
+require "net/https"
+require "json"
 
 require_relative "telebugs/version"
 require_relative "telebugs/config"
 require_relative "telebugs/promise"
+require_relative "telebugs/notifier"
+require_relative "telebugs/sender"
 require_relative "telebugs/wrapped_error"
+require_relative "telebugs/notice"
 
 module Telebugs
   # The general error that this library uses when it wants to raise.
   Error = Class.new(StandardError)
 
+  HTTPError = Class.new(Error)
+
   class << self
     def configure
-      yield Telebugs::Config.instance
+      yield Config.instance
     end
 
     def notify(error:)
-      Telebugs::Promise.new(error) do
-      end
+      Notifier.instance.notify(error)
     end
   end
 end
diff --git a/lib/telebugs/config.rb b/lib/telebugs/config.rb
index 95c1c36..7bf0e08 100644
--- a/lib/telebugs/config.rb
+++ b/lib/telebugs/config.rb
@@ -4,7 +4,10 @@ module Telebugs
   # Represents the Telebugs config. A config contains all the options that you
   # can use to configure a +Telebugs::Notifier+ instance.
   class Config
+    ERROR_API_URL = "https://api.telebugs.com/2024-03-28/errors"
+
     attr_accessor :api_key
+    attr_reader :api_url
 
     class << self
       attr_writer :instance
@@ -15,7 +18,16 @@ def instance
     end
 
     def initialize
-      @api_key = nil
+      reset
+    end
+
+    def api_url=(url)
+      @api_url = URI(url)
+    end
+
+    def reset
+      self.api_key = nil
+      self.api_url = ERROR_API_URL
     end
   end
 end
diff --git a/lib/telebugs/notice.rb b/lib/telebugs/notice.rb
new file mode 100644
index 0000000..ab8a98c
--- /dev/null
+++ b/lib/telebugs/notice.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+module Telebugs
+  # Represents a piece of information that will be sent to Telebugs API to
+  # report an error.
+  class Notice
+    # The list of possible exceptions that might be raised when an object is
+    # converted to JSON
+    JSON_EXCEPTIONS = [
+      IOError,
+      NotImplementedError,
+      JSON::GeneratorError,
+      Encoding::UndefinedConversionError
+    ].freeze
+
+    # On Ruby 3.1+, the error highlighting gem can produce messages that can
+    # span over multiple lines. We don't want to display multiline error titles.
+    # Therefore, we want to strip out the higlighting part so that the errors
+    # look consistent.
+    RUBY_31_ERROR_HIGHLIGHTING_DIVIDER = "\n\n"
+
+    # The options for +String#encode+
+    ENCODING_OPTIONS = {invalid: :replace, undef: :replace}.freeze
+
+    # The maxium size of the JSON payload in bytes
+    MAX_NOTICE_SIZE = 64000
+
+    def initialize(error)
+      @payload = {
+        errors: errors_as_json(error)
+      }
+    end
+
+    # Converts the notice to JSON. Calls +to_json+ on each object inside
+    # notice's payload. Truncates notices, JSON representation of which is
+    # bigger than {MAX_NOTICE_SIZE}.
+    def to_json(*_args)
+      loop do
+        begin
+          json = @payload.to_json
+        rescue *JSON_EXCEPTIONS
+          # TODO
+        else
+          return json if json && json.bytesize <= MAX_NOTICE_SIZE
+        end
+
+        break if truncate == 0
+      end
+    end
+
+    private
+
+    def errors_as_json(error)
+      WrappedError.new(error).unwrap.map do |e|
+        {
+          type: e.class.name,
+          message: message(e)
+        }
+      end
+    end
+
+    def message(error)
+      return unless (msg = error.message)
+
+      msg.encode(Encoding::UTF_8, **ENCODING_OPTIONS)
+        .split(RUBY_31_ERROR_HIGHLIGHTING_DIVIDER)
+        .first
+    end
+
+    def truncate
+      0
+    end
+  end
+end
diff --git a/lib/telebugs/notifier.rb b/lib/telebugs/notifier.rb
new file mode 100644
index 0000000..0d3e4fc
--- /dev/null
+++ b/lib/telebugs/notifier.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Telebugs
+  # Notifier is reponsible for sending notices to Telebugs.
+  class Notifier
+    class << self
+      attr_writer :instance
+
+      def instance
+        @instance ||= new
+      end
+    end
+
+    def initialize
+      @sender = Sender.new
+    end
+
+    def notify(error)
+      Telebugs::Promise.new(error) do
+        @sender.send(error)
+      end
+    end
+  end
+end
diff --git a/lib/telebugs/promise.rb b/lib/telebugs/promise.rb
index 8026658..d34a73e 100644
--- a/lib/telebugs/promise.rb
+++ b/lib/telebugs/promise.rb
@@ -11,5 +11,21 @@ def initialize(...)
     def value
       @future.value
     end
+
+    def reason
+      @future.reason
+    end
+
+    def wait
+      @future.wait
+    end
+
+    def fulfilled?
+      @future.fulfilled?
+    end
+
+    def rejected?
+      @future.rejected?
+    end
   end
 end
diff --git a/lib/telebugs/sender.rb b/lib/telebugs/sender.rb
new file mode 100644
index 0000000..14c4bf8
--- /dev/null
+++ b/lib/telebugs/sender.rb
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+module Telebugs
+  # Responsible for sending HTTP requests to Telebugs.
+  class Sender
+    CONTENT_TYPE = "application/json"
+
+    USER_AGENT = "telebugs-ruby/#{Telebugs::VERSION} (#{RUBY_ENGINE}/#{RUBY_VERSION})"
+
+    def initialize
+      @config = Config.instance
+      @authorization = "Bearer #{@config.api_key}"
+    end
+
+    def send(data)
+      req = build_request(@config.api_url, data)
+
+      resp = build_https(@config.api_url).request(req)
+      if resp.code_type == Net::HTTPCreated
+        return JSON.parse(resp.body)
+      end
+
+      raise HTTPError, "#{resp.code_type} (#{resp.code}): #{JSON.parse(resp.body)}"
+    end
+
+    private
+
+    def build_request(uri, data)
+      Net::HTTP::Post.new(uri.request_uri).tap do |req|
+        req["Authorization"] = @authorization
+        req["Content-Type"] = CONTENT_TYPE
+        req["User-Agent"] = USER_AGENT
+
+        req.body = data.to_json
+      end
+    end
+
+    def build_https(uri)
+      Net::HTTP.new(uri.host, uri.port).tap do |https|
+        https.use_ssl = uri.is_a?(URI::HTTPS)
+      end
+    end
+  end
+end
diff --git a/telebugs.gemspec b/telebugs.gemspec
index d49d1f5..88e8ce4 100644
--- a/telebugs.gemspec
+++ b/telebugs.gemspec
@@ -34,6 +34,8 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency "concurrent-ruby", "~> 1.3"
 
+  spec.add_development_dependency "webmock", "~> 3.23"
+
   # For more information and examples about making a new gem, check out our
   # guide at: https://bundler.io/guides/creating_gem.html
   spec.metadata["rubygems_mfa_required"] = "true"
diff --git a/test/test_config.rb b/test/test_config.rb
new file mode 100644
index 0000000..3a79076
--- /dev/null
+++ b/test/test_config.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class TestConfig < Minitest::Test
+  def teardown
+    Telebugs::Config.instance.reset
+  end
+
+  def test_api_key
+    Telebugs.configure { |c| c.api_key = "12345:abcdef" }
+
+    assert_equal "12345:abcdef", Telebugs::Config.instance.api_key
+  end
+
+  def test_error_api_url
+    Telebugs.configure { |c| c.api_url = "example.com" }
+
+    assert_equal URI("example.com"), Telebugs::Config.instance.api_url
+  end
+end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index e7aeea9..230068c 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -4,3 +4,4 @@
 require "telebugs"
 
 require "minitest/autorun"
+require "webmock/minitest"
diff --git a/test/test_notice.rb b/test/test_notice.rb
new file mode 100644
index 0000000..ebb8bb1
--- /dev/null
+++ b/test/test_notice.rb
@@ -0,0 +1,89 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class TestNotice < Minitest::Test
+  def test_to_json_with_nested_errors
+    begin
+      raise StandardError.new("error 1")
+    rescue => _
+      begin
+        raise StandardError.new("error 2")
+      rescue => e2
+        n = Telebugs::Notice.new(e2)
+      end
+    end
+
+    assert_equal(
+      {
+        "errors" => [
+          {
+            "type" => "StandardError",
+            "message" => "error 2"
+          },
+          {
+            "type" => "StandardError",
+            "message" => "error 1"
+          }
+        ]
+      },
+      JSON.parse(n.to_json)
+    )
+  end
+
+  def test_to_json_with_error_highlighting_in_messages
+    begin
+      raise "undefined method `[]' for nil:NilClass\n\n    " \
+            "data[:result].first[:first_name]\n                       ^^^^^^^^^^^^^"
+    rescue => e
+    end
+
+    n = Telebugs::Notice.new(e)
+
+    assert_equal(
+      {
+        "errors" => [
+          {
+            "type" => "RuntimeError",
+            "message" => "undefined method `[]' for nil:NilClass"
+          }
+        ]
+      },
+      JSON.parse(n.to_json)
+    )
+  end
+
+  def test_to_json_when_error_message_contains_invalid_characters
+    begin
+      JSON.parse(Marshal.dump(Time.now))
+    rescue JSON::ParserError => e
+    end
+
+    n = Telebugs::Notice.new(e)
+    json = JSON.parse(n.to_json)
+
+    assert_equal "JSON::ParserError", json["errors"].first["type"]
+    assert_match(/unexpected token at/, json["errors"].first["message"])
+  end
+
+  def test_to_json_when_error_message_is_nil
+    error = Class.new(StandardError) {
+      def message
+      end
+    }.new
+
+    n = Telebugs::Notice.new(error)
+
+    assert_equal(
+      {
+        "errors" => [
+          {
+            "type" => nil,
+            "message" => nil
+          }
+        ]
+      },
+      JSON.parse(n.to_json)
+    )
+  end
+end
diff --git a/test/test_notifier.rb b/test/test_notifier.rb
new file mode 100644
index 0000000..f68fced
--- /dev/null
+++ b/test/test_notifier.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class TestNotifier < Minitest::Test
+  def teardown
+    WebMock.reset!
+  end
+
+  def test_notify_returns_a_promise_that_resolves_to_a_hash
+    stub_request(:post, Telebugs::Config.instance.api_url)
+      .to_return(status: 201, body: {id: "123"}.to_json)
+
+    p = Telebugs::Notifier.new.notify(StandardError.new)
+
+    assert_equal({"id" => "123"}, p.value)
+  end
+end
diff --git a/test/test_promise.rb b/test/test_promise.rb
index b03f40c..3c97798 100644
--- a/test/test_promise.rb
+++ b/test/test_promise.rb
@@ -3,9 +3,29 @@
 require "test_helper"
 
 class TestPromise < Minitest::Test
-  def test_future_value
-    promise = Telebugs::Promise.new { 1 + 1 }
+  def test_value
+    p = Telebugs::Promise.new { 1 + 1 }
 
-    assert_equal 2, promise.value
+    assert_equal 2, p.value
+  end
+
+  def test_reason
+    p = Telebugs::Promise.new { raise "error" }
+
+    assert_equal "error", p.reason.message
+  end
+
+  def test_fulfilled
+    p = Telebugs::Promise.new { 1 + 1 }
+    p.wait
+
+    assert p.fulfilled?
+  end
+
+  def test_rejected
+    p = Telebugs::Promise.new { raise "error" }
+    p.wait
+
+    assert p.rejected?
   end
 end
diff --git a/test/test_sender.rb b/test/test_sender.rb
new file mode 100644
index 0000000..710f24d
--- /dev/null
+++ b/test/test_sender.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class TestSender < Minitest::Test
+  def teardown
+    Telebugs::Config.instance.reset
+    WebMock.reset!
+  end
+
+  def test_send_attaches_correct_authorization_headers
+    Telebugs.configure { |c| c.api_key = "12345:abcdef" }
+
+    stub = stub_request(:post, Telebugs::Config.instance.api_url)
+      .to_return(status: 201, body: {id: "123"}.to_json)
+
+    Telebugs::Sender.new.send({"errors" => []})
+
+    assert_requested stub.with(
+      headers: {
+        "Authorization" => "Bearer 12345:abcdef",
+        "Content-Type" => "application/json",
+        "User-Agent" => "telebugs-ruby/#{Telebugs::VERSION} (ruby/#{RUBY_VERSION})"
+      },
+      body: {"errors" => []}.to_json
+    )
+  end
+
+  def test_send_raises_http_error_when_response_code_is_not_created
+    stub = stub_request(:post, Telebugs::Config.instance.api_url)
+      .to_return(status: 500, body: {"error" => "oops"}.to_json)
+
+    assert_raises(Telebugs::HTTPError) do
+      Telebugs::Sender.new.send({"errors" => []})
+    end
+
+    assert_requested stub
+  end
+end
diff --git a/test/test_telebugs.rb b/test/test_telebugs.rb
index 3170d26..9585329 100644
--- a/test/test_telebugs.rb
+++ b/test/test_telebugs.rb
@@ -3,6 +3,11 @@
 require "test_helper"
 
 class TestTelebugs < Minitest::Test
+  def teardown
+    Telebugs::Config.instance.reset
+    WebMock.reset!
+  end
+
   def test_that_it_has_a_version_number
     refute_nil ::Telebugs::VERSION
   end
@@ -17,9 +22,22 @@ def test_configure_configures_project_key
     assert_equal key, Telebugs::Config.instance.api_key
   end
 
-  def test_notify_returns_a_future
-    future = Telebugs.notify(error: StandardError.new)
+  def test_notify_returns_a_fullfilled_promise_when_request_succeeds
+    stub_request(:post, Telebugs::Config.instance.api_url)
+      .to_return(status: 201, body: {id: "123"}.to_json)
+
+    p = Telebugs.notify(error: StandardError.new)
+    p.wait
+
+    assert p.fulfilled?
+  end
+
+  def test_notify_returns_a_rejected_promise_when_request_fails
+    stub_request(:post, Telebugs::Config.instance.api_url).to_return(status: 500)
+
+    p = Telebugs.notify(error: StandardError.new)
+    p.wait
 
-    assert_instance_of Telebugs::Promise, future
+    assert p.rejected?
   end
 end