PhoenixApiDocs generates API documentation from annotations in controllers actions and tests cases.



Phoenix Api Docs

PhoenixApiDocs is a library written in the Elixir for the Phoenix framework. It lets you generate API documentation in the API Blueprint format from annotations in controllers and automated tests.


Add PhoenixApiDocs to your mix.exs dependencies:

defp deps do
  [{:phoenix_api_docs, "~> 0.1.0"}]

Run mix deps.get to fetch the dependencies:

$ mix deps.get

In your test/test_helper.exs start gen server PhoenixApiDocs.start for logging requests and configure ExUnit to use PhoenixApiDocs.Formatter:

ExUnit.start(formatters: [ExUnit.CLIFormatter, PhoenixApiDocs.Formatter])


Add PhoenixApiDocs.Controller to your phoenix controller and use api\3 macro to generate specification for the controller action:

defmodule App.CommentController do
  use App.Web, :controller
  use PhoenixApiDocs.Controller

  api :GET, "/posts/:post_id/comments" do
    group "Comment" # If not provided, it will be guessed from the controller name (resource name)
    title "List comments for specific docs"
    description "Optiona description that will be displayed in the documentation"
    note "Optional note that will be displayed in the documentation"
    parameter :post_id, :integer, :required, "Post ID or slug"
  def index(conn, %{"post_id" => post_id}) do

  api :PUT, "/posts/:post_id/comments" do
    title "Update comment"
    parameter :post_id, :integer, :required, "Post ID or slug"
  def update(conn, %{"comment" => comment_params}) do


API specification options:

  • method: HTTP method - GET, POST, PUT, PATCH, DELETE
  • url: URL route from phoenix router`
  • group: Documentation routes are grouped by a group name (defaults to resource name guessed from the controller name)
  • title: Title (can use Blueprint format)
  • description: Description (optional, can use Blueprint format)
  • note: Note (optional, can use Blueprint format)
  • parameter: name, type, required/optional, description
    • required - parameter :post_id, :integer, :required, "Post ID"
    • optional - parameter :post_id, :integer, "Post ID"

In your tests select what requests and responses you want to include in the documentation by saving conn to PhoenixApiDocs.ConnLogger:

  test "list comments for post", %{conn: conn} do
    post = insert(:post)
    insert_list(5, :comment, post: post)

    conn = get(
      comments_path(conn, :index, post)

    assert json_response(conn, 200)
  end can be also piped:

    conn = get(
      comments_path(conn, :index, post)
    ) |>

After you run your tests, documentation in an API Blueprint format will be generate in a file api.apib

$ mix test

To generate the documentation in a HTML format use Aglio renderer

$ npm install aglio -g

$ mix phoenix.api_docs


The configuration options can be setup in config.exs:

config :phoenix_api_docs,
  docs_path: "priv/static/docs",
  theme: "triple"

Config options:

  • :docs_path: Specify the path where the documentation will be generated. If you want to serve the documentation directly from the phoenix you can specify priv/static/docs.
  • :theme: HTML theme is generated using the Aglio renderer.

Common problems

Route is not generated after adding api annotation in the controller

Please make sure that the route you are using in the annotation matches exactly the route from the phoenix router (including params). Run mix phoenix.routes and compare the routes.

Tasks to do

  • raise error when route that is used in the annotation is not available in the phoenix router