diff --git a/CHANGELOG.md b/CHANGELOG.md
index ee003e8..56dafdf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,3 +10,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Initialise repository.
+
+## [0.1.0] - 2023-07-18
+
+### Changed
+
+- Got the gem working with the API. MVP
diff --git a/Gemfile.lock b/Gemfile.lock
index 3b2c661..851fcdc 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    anthropic (0.0.0)
+    anthropic (0.1.0)
       faraday (>= 1)
       faraday-multipart (>= 1)
 
diff --git a/README.md b/README.md
index 812f04e..6f9565d 100644
--- a/README.md
+++ b/README.md
@@ -4,9 +4,9 @@
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/alexrudall/anthropic/blob/main/LICENSE.txt)
 [![CircleCI Build Status](https://circleci.com/gh/alexrudall/anthropic.svg?style=shield)](https://circleci.com/gh/alexrudall/anthropic)
 
-Use the [Anthropic API](https://anthropic.com/blog/anthropic-api/) with Ruby! 🤖❤️
+Use the [Anthropic API](https://docs.anthropic.com/claude/reference/getting-started-with-the-api) with Ruby! 🌌❤️
 
-This is very much a WIP and probably doesn't work as I don't have access to the Anthropic API as yet, but it will get a lot better once I do! Hopefully very soon :D
+You can apply for access to the API [here](https://docs.anthropic.com/claude/docs/getting-access-to-claude).
 
 [Ruby AI Builders Discord](https://discord.gg/k4Uc224xVD)
 
@@ -40,8 +40,7 @@ require "anthropic"
 
 ## Usage
 
-- Get your API key from [https://platform.anthropic.com/account/api-keys](https://platform.anthropic.com/account/api-keys)
-- If you belong to multiple organizations, you can get your Organization ID from [https://platform.anthropic.com/account/org-settings](https://platform.anthropic.com/account/org-settings)
+- Get your API key from [https://console.anthropic.com/account/keys](https://console.anthropic.com/account/keys)
 
 ### Quickstart
 
@@ -67,26 +66,27 @@ Then you can create a client like this:
 client = Anthropic::Client.new
 ```
 
-#### Custom timeout or base URI
+#### Change version or timeout
+
+You can change to a different dated version (different from the URL version which is just `v1`) of Anthropic's API by passing `anthropic_version` when initializing the client. If you don't the default latest will be used, which is "2023-06-01". [More info](https://docs.anthropic.com/claude/reference/versioning)
 
 The default timeout for any request using this library is 120 seconds. You can change that by passing a number of seconds to the `request_timeout` when initializing the client.
 
 ```ruby
 client = Anthropic::Client.new(
     access_token: "access_token_goes_here",
-    request_timeout: 240
+    anthropic_version: "2023-01-01", # Optional
+    request_timeout: 240 # Optional
 )
 ```
 
-or when configuring the gem:
+You can also set these keys when configuring the gem:
 
 ```ruby
 Anthropic.configure do |config|
     config.access_token = ENV.fetch("ANTHROPIC_API_KEY")
+    config.anthropic_version = "2023-01-01" # Optional
     config.request_timeout = 240 # Optional
-    config.extra_headers = {
-        "X-Proxy-Refresh": "true"
-    } # Optional
 end
 ```
 
@@ -95,16 +95,30 @@ end
 Hit the Anthropic API for a completion:
 
 ```ruby
-response = client.completions(
+response = client.complete(
     parameters: {
         model: "claude-2",
-        prompt: "Once upon a time",
-        max_tokens: 5
+        prompt: "How high is the sky?",
+        max_tokens_to_sample: 5
     })
-puts response["choices"].map { |c| c["text"] }
-# => [", there lived a great"]
+puts response["completion"]
+# => " The sky has no definitive"
 ```
 
+Note that all requests are prepended by this library with
+
+`\n\nHuman: `
+
+and appended with
+
+`\n\nAssistant:`
+
+so whatever prompt you pass will be sent to the API as
+
+`\n\nHuman: How high is the sky?\n\nAssistant:`
+
+This is a requirement of [the API](https://docs.anthropic.com/claude/reference/complete_post).
+
 ## Development
 
 After checking out the repo, run `bin/setup` to install dependencies. You can run `bin/console` for an interactive prompt that will allow you to experiment.
diff --git a/anthropic.gemspec b/anthropic.gemspec
index a05d4c3..fe94571 100644
--- a/anthropic.gemspec
+++ b/anthropic.gemspec
@@ -6,7 +6,7 @@ Gem::Specification.new do |spec|
   spec.authors       = ["Alex"]
   spec.email         = ["alexrudall@users.noreply.github.com"]
 
-  spec.summary       = "Anthropic API + Ruby! 🤖❤️"
+  spec.summary       = "Anthropic API + Ruby! 🌌❤️"
   spec.homepage      = "https://github.com/alexrudall/anthropic"
   spec.license       = "MIT"
   spec.required_ruby_version = Gem::Requirement.new(">= 2.6.0")
diff --git a/lib/anthropic.rb b/lib/anthropic.rb
index 0c8f87a..9a6fc29 100644
--- a/lib/anthropic.rb
+++ b/lib/anthropic.rb
@@ -3,10 +3,6 @@
 
 require_relative "anthropic/http"
 require_relative "anthropic/client"
-require_relative "anthropic/files"
-require_relative "anthropic/finetunes"
-require_relative "anthropic/images"
-require_relative "anthropic/models"
 require_relative "anthropic/version"
 
 module Anthropic
@@ -15,15 +11,18 @@ class ConfigurationError < Error; end
 
   class Configuration
     attr_writer :access_token
-    attr_accessor :api_version, :organization_id, :uri_base, :request_timeout, :extra_headers
+    attr_accessor :anthropic_version, :api_version, :extra_headers, :organization_id,
+                  :request_timeout, :uri_base
 
     DEFAULT_API_VERSION = "v1".freeze
+    DEFAULT_ANTHROPIC_VERSION = "2023-06-01".freeze
     DEFAULT_URI_BASE = "https://api.anthropic.com/".freeze
     DEFAULT_REQUEST_TIMEOUT = 120
 
     def initialize
       @access_token = nil
       @api_version = DEFAULT_API_VERSION
+      @anthropic_version = DEFAULT_ANTHROPIC_VERSION
       @organization_id = nil
       @uri_base = DEFAULT_URI_BASE
       @request_timeout = DEFAULT_REQUEST_TIMEOUT
diff --git a/lib/anthropic/client.rb b/lib/anthropic/client.rb
index 349b771..3ea291d 100644
--- a/lib/anthropic/client.rb
+++ b/lib/anthropic/client.rb
@@ -11,8 +11,19 @@ def initialize(access_token: nil, organization_id: nil, uri_base: nil, request_t
       Anthropic.configuration.extra_headers = extra_headers
     end
 
-    def completions(parameters: {})
-      Anthropic::Client.json_post(path: "/completions", parameters: parameters)
+    def complete(parameters: {})
+      parameters[:prompt] = wrap_prompt(prompt: parameters[:prompt])
+      Anthropic::Client.json_post(path: "/complete", parameters: parameters)
+    end
+
+    private
+
+    def wrap_prompt(prompt:, prefix: "\n\nHuman: ", suffix: "\n\nAssistant:")
+      return if prompt.nil?
+
+      prompt.prepend(prefix) unless prompt.start_with?(prefix)
+      prompt.concat(suffix) unless prompt.end_with?(suffix)
+      prompt
     end
   end
 end
diff --git a/lib/anthropic/http.rb b/lib/anthropic/http.rb
index 075867d..4a72c04 100644
--- a/lib/anthropic/http.rb
+++ b/lib/anthropic/http.rb
@@ -74,8 +74,8 @@ def uri(path:)
     def headers
       {
         "Content-Type" => "application/json",
-        "Authorization" => "Bearer #{Anthropic.configuration.access_token}",
-        "Anthropic-Organization" => Anthropic.configuration.organization_id
+        "x-api-key" => Anthropic.configuration.access_token,
+        "Anthropic-Version" => Anthropic.configuration.anthropic_version
       }.merge(Anthropic.configuration.extra_headers)
     end
 
@@ -83,7 +83,7 @@ def multipart_parameters(parameters)
       parameters&.transform_values do |value|
         next value unless value.is_a?(File)
 
-        # Doesn't seem like Anthropic need mime_type yet, so not worth
+        # Doesn't seem like Anthropic needs mime_type yet, so not worth
         # the library to figure this out. Hence the empty string
         # as the second argument.
         Faraday::UploadIO.new(value, "", value.path)
diff --git a/lib/anthropic/version.rb b/lib/anthropic/version.rb
index 0c18896..8665306 100644
--- a/lib/anthropic/version.rb
+++ b/lib/anthropic/version.rb
@@ -1,3 +1,3 @@
 module Anthropic
-  VERSION = "0.0.0".freeze
+  VERSION = "0.1.0".freeze
 end
diff --git a/spec/anthropic/client/complete_spec.rb b/spec/anthropic/client/complete_spec.rb
new file mode 100644
index 0000000..0eab12d
--- /dev/null
+++ b/spec/anthropic/client/complete_spec.rb
@@ -0,0 +1,30 @@
+RSpec.describe Anthropic::Client do
+  describe "#complete" do
+    context "with a prompt and max_tokens", :vcr do
+      let(:prompt) { "How high is the sky?" }
+      let(:max_tokens) { 5 }
+
+      let(:response) do
+        Anthropic::Client.new.complete(
+          parameters: {
+            model: model,
+            max_tokens_to_sample: max_tokens,
+            prompt: prompt
+          }
+        )
+      end
+      let(:text) { response.dig("choices", 0, "text") }
+      let(:cassette) { "#{model} complete #{prompt}".downcase }
+
+      context "with model: claude-2" do
+        let(:model) { "claude-2" }
+
+        it "succeeds" do
+          VCR.use_cassette(cassette) do
+            expect(response["completion"].empty?).to eq(false)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/anthropic_spec.rb b/spec/anthropic_spec.rb
new file mode 100644
index 0000000..9b54677
--- /dev/null
+++ b/spec/anthropic_spec.rb
@@ -0,0 +1,58 @@
+RSpec.describe Anthropic do
+  it "has a version number" do
+    expect(Anthropic::VERSION).not_to be nil
+  end
+
+  describe "#configure" do
+    let(:access_token) { "abc123" }
+    let(:api_version) { "v2" }
+    let(:organization_id) { "def456" }
+    let(:custom_uri_base) { "ghi789" }
+    let(:custom_request_timeout) { 25 }
+    let(:extra_headers) { { "User-Agent" => "Anthropic Ruby Gem #{Anthropic::VERSION}" } }
+
+    before do
+      Anthropic.configure do |config|
+        config.access_token = access_token
+        config.api_version = api_version
+        config.organization_id = organization_id
+        config.extra_headers = extra_headers
+      end
+    end
+
+    it "returns the config" do
+      expect(Anthropic.configuration.access_token).to eq(access_token)
+      expect(Anthropic.configuration.api_version).to eq(api_version)
+      expect(Anthropic.configuration.organization_id).to eq(organization_id)
+      expect(Anthropic.configuration.uri_base).to eq("https://api.anthropic.com/")
+      expect(Anthropic.configuration.request_timeout).to eq(120)
+      expect(Anthropic.configuration.extra_headers).to eq(extra_headers)
+    end
+
+    context "without an access token" do
+      let(:access_token) { nil }
+
+      it "raises an error" do
+        expect { Anthropic::Client.new.complete }.to raise_error(Anthropic::ConfigurationError)
+      end
+    end
+
+    context "with custom timeout and uri base" do
+      before do
+        Anthropic.configure do |config|
+          config.uri_base = custom_uri_base
+          config.request_timeout = custom_request_timeout
+        end
+      end
+
+      it "returns the config" do
+        expect(Anthropic.configuration.access_token).to eq(access_token)
+        expect(Anthropic.configuration.api_version).to eq(api_version)
+        expect(Anthropic.configuration.organization_id).to eq(organization_id)
+        expect(Anthropic.configuration.uri_base).to eq(custom_uri_base)
+        expect(Anthropic.configuration.request_timeout).to eq(custom_request_timeout)
+        expect(Anthropic.configuration.extra_headers).to eq(extra_headers)
+      end
+    end
+  end
+end
diff --git a/spec/compatibility_spec.rb b/spec/compatibility_spec.rb
new file mode 100644
index 0000000..848f41b
--- /dev/null
+++ b/spec/compatibility_spec.rb
@@ -0,0 +1,33 @@
+RSpec.describe "compatibility" do
+  context "for moved constants" do
+    describe "::Ruby::Anthropic::VERSION" do
+      it "is mapped to ::Anthropic::VERSION" do
+        expect(Ruby::Anthropic::VERSION).to eq(Anthropic::VERSION)
+      end
+    end
+
+    describe "::Ruby::Anthropic::Error" do
+      it "is mapped to ::Anthropic::Error" do
+        expect(Ruby::Anthropic::Error).to eq(Anthropic::Error)
+        expect(Ruby::Anthropic::Error.new).to be_a(Anthropic::Error)
+        expect(Anthropic::Error.new).to be_a(Ruby::Anthropic::Error)
+      end
+    end
+
+    describe "::Ruby::Anthropic::ConfigurationError" do
+      it "is mapped to ::Anthropic::ConfigurationError" do
+        expect(Ruby::Anthropic::ConfigurationError).to eq(Anthropic::ConfigurationError)
+        expect(Ruby::Anthropic::ConfigurationError.new).to be_a(Anthropic::ConfigurationError)
+        expect(Anthropic::ConfigurationError.new).to be_a(Ruby::Anthropic::ConfigurationError)
+      end
+    end
+
+    describe "::Ruby::Anthropic::Configuration" do
+      it "is mapped to ::Anthropic::Configuration" do
+        expect(Ruby::Anthropic::Configuration).to eq(Anthropic::Configuration)
+        expect(Ruby::Anthropic::Configuration.new).to be_a(Anthropic::Configuration)
+        expect(Anthropic::Configuration.new).to be_a(Ruby::Anthropic::Configuration)
+      end
+    end
+  end
+end
diff --git a/spec/fixtures/cassettes/claude-2_complete_how_high_is_the_sky_.yml b/spec/fixtures/cassettes/claude-2_complete_how_high_is_the_sky_.yml
new file mode 100644
index 0000000..6f989b0
--- /dev/null
+++ b/spec/fixtures/cassettes/claude-2_complete_how_high_is_the_sky_.yml
@@ -0,0 +1,48 @@
+---
+http_interactions:
+- request:
+    method: post
+    uri: https://api.anthropic.com/v1/complete
+    body:
+      encoding: UTF-8
+      string: '{"model":"claude-2","max_tokens_to_sample":5,"prompt":"\n\nHuman: How
+        high is the sky?\n\nAssistant:"}'
+    headers:
+      Content-Type:
+      - application/json
+      X-Api-Key:
+      - "<ANTHROPIC_API_KEY>"
+      Anthropic-Version:
+      - '2023-06-01'
+      Accept-Encoding:
+      - gzip;q=1.0,deflate;q=0.6,identity;q=0.3
+      Accept:
+      - "*/*"
+      User-Agent:
+      - Ruby
+  response:
+    status:
+      code: 200
+      message: OK
+    headers:
+      Content-Type:
+      - application/json
+      Request-Id:
+      - b5a12f0ec9900c47ed5c9254d2794f72c14afa6c61571a11ce33f45034ae7bce
+      X-Cloud-Trace-Context:
+      - 10e11e101cb2e344ac40eb006d258e04
+      Date:
+      - Tue, 18 Jul 2023 13:42:05 GMT
+      Server:
+      - Google Frontend
+      Content-Length:
+      - '179'
+      Via:
+      - 1.1 google
+      Alt-Svc:
+      - h3=":443"; ma=2592000,h3-29=":443"; ma=2592000
+    body:
+      encoding: UTF-8
+      string: '{"completion":" The sky has no definitive","stop_reason":"max_tokens","model":"claude-2.0","stop":null,"log_id":"b5a12f0ec9900c47ed5c9254d2794f72c14afa6c61571a11ce33f45034ae7bce"}'
+  recorded_at: Tue, 18 Jul 2023 13:42:05 GMT
+recorded_with: VCR 6.1.0
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
new file mode 100644
index 0000000..53df2ce
--- /dev/null
+++ b/spec/spec_helper.rb
@@ -0,0 +1,47 @@
+require "bundler/setup"
+require "dotenv/load"
+require "anthropic"
+require "anthropic/compatibility"
+require "vcr"
+
+Dir[File.expand_path("spec/support/**/*.rb")].sort.each { |f| require f }
+
+VCR.configure do |c|
+  c.hook_into :webmock
+  c.cassette_library_dir = "spec/fixtures/cassettes"
+  c.default_cassette_options = {
+    record: ENV.fetch("ANTHROPIC_API_KEY", nil) ? :all : :new_episodes,
+    match_requests_on: [:method, :uri, VCRMultipartMatcher.new]
+  }
+  c.filter_sensitive_data("<ANTHROPIC_API_KEY>") { Anthropic.configuration.access_token }
+end
+
+RSpec.configure do |c|
+  # Enable flags like --only-failures and --next-failure
+  c.example_status_persistence_file_path = ".rspec_status"
+
+  # Disable RSpec exposing methods globally on `Module` and `main`
+  c.disable_monkey_patching!
+
+  c.expect_with :rspec do |rspec|
+    rspec.syntax = :expect
+  end
+
+  if ENV.fetch("ANTHROPIC_API_KEY", nil)
+    warning = "WARNING! Specs are hitting the Anthropic API using your ANTHROPIC_API_KEY! This
+costs at least 2 cents per run and is very slow! If you don't want this, unset
+ANTHROPIC_API_KEY to just run against the stored VCR responses.".freeze
+    warning = RSpec::Core::Formatters::ConsoleCodes.wrap(warning, :bold_red)
+
+    c.before(:suite) { RSpec.configuration.reporter.message(warning) }
+    c.after(:suite) { RSpec.configuration.reporter.message(warning) }
+  end
+
+  c.before(:all) do
+    Anthropic.configure do |config|
+      config.access_token = ENV.fetch("ANTHROPIC_API_KEY", "dummy-token")
+    end
+  end
+end
+
+RSPEC_ROOT = File.dirname __FILE__
diff --git a/spec/support/vcr_multipart_matcher.rb b/spec/support/vcr_multipart_matcher.rb
new file mode 100644
index 0000000..4e51da6
--- /dev/null
+++ b/spec/support/vcr_multipart_matcher.rb
@@ -0,0 +1,47 @@
+class VCRMultipartMatcher
+  MULTIPART_HEADER_MATCHER = %r{^multipart/form-data; boundary=(.+)$}.freeze
+  BOUNDARY_SUBSTITUTION = "----MultipartBoundaryAbcD3fGhiXyz00001".freeze
+
+  def call(request1, request2)
+    return false unless same_content_type?(request1, request2)
+    unless headers_excluding_content_type(request1) == headers_excluding_content_type(request2)
+      return false
+    end
+
+    normalized_multipart_body(request1) == normalized_multipart_body(request2)
+  end
+
+  private
+
+  def same_content_type?(request1, request2)
+    content_type1 = (request1.headers["Content-Type"] || []).first.to_s
+    content_type2 = (request2.headers["Content-Type"] || []).first.to_s
+
+    if multipart_request?(content_type1)
+      multipart_request?(content_type2)
+    elsif multipart_request?(content_type2)
+      false
+    else
+      content_type1 == content_type2
+    end
+  end
+
+  def headers_excluding_content_type(request)
+    request.headers.reject { |key, _| key == "Content-Type" }
+  end
+
+  def normalized_multipart_body(request)
+    content_type = (request.headers["Content-Type"] || []).first.to_s
+
+    return request.headers unless multipart_request?(content_type)
+
+    boundary = MULTIPART_HEADER_MATCHER.match(content_type)[1]
+    request.body.gsub(boundary, BOUNDARY_SUBSTITUTION)
+  end
+
+  def multipart_request?(content_type)
+    return false if content_type.empty?
+
+    MULTIPART_HEADER_MATCHER.match?(content_type)
+  end
+end