diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index cbae2337..9ad5c756 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -17,13 +17,10 @@ To test with a real GitHub repository, you'll need to create a test repository a
   - **Payload URL:** Use the full `*.ngrok.io`
   - **Secret:** `development`
   - **Which events would you like to trigger this webhook?:** Choose **Send me everything**.
-0. Create a `.probot.yml` in your repo with:
+0. Create a `.probot` in your repo with:
+
+        on issues.opened then comment("Hello World! Your bot is working!");
 
-        behaviors:
-        - on: issues.opened
-          then:
-            comment: "Hello World! Your bot is working!"
-        
 0. Open a new issue. Your bot should post a comment (you may need to refresh to see it).
 
 ## Debugging
diff --git a/README.md b/README.md
index 639facef..21b56abd 100644
--- a/README.md
+++ b/README.md
@@ -12,16 +12,9 @@ _**Heads up!** The [demo integration](https://github.com/integration/probot-demo
 
 0. Go to the **[demo integration](https://github.com/integration/probot-demo)**, click **Install**, and then select an organization.
 0. Add @probot as a collaborator with write access on your repository.
-0. Create a `.probot.yml` file in your repository with the following contents. See [Configuration](docs/configuration.md) for more information on what behaviors can be built.
+0. Create a `.probot` file in your repository with the following contents. See [Configuration](docs/configuration.md) for more information on what behaviors can be built.
 
-        behaviors:
-          - on: issues.opened
-            then:
-              comment: >
-                Hello @{{ sender.login }}. Thanks for inviting me to your project. Read
-                more about [all the things I can help you with][config]. I can't wait to
-                get started!
-
-                [config]: https://github.com/bkeepers/PRobot/blob/master/docs/configuration.md
+        on issues.opened
+        then comment("Hello @{{ sender.login }}. Thanks for inviting me to your project. Read more about [all the things I can help you with][config]. I can't wait to get started!\\n[config]: https://github.com/bkeepers/PRobot/blob/master/docs/configuration.md");
 
 0. Open a new issue. @probot should post a comment (you may need to refresh to see it).
diff --git a/docs/configuration.md b/docs/configuration.md
index 6b99fe14..ed70744d 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -2,23 +2,18 @@
 
 _**Heads up!** This yaml-based configuration syntax is not great. Ideally it will be replaced by a [proper grammar](https://github.com/bkeepers/PRobot/issues/35)._
 
-Behaviors are configured in a file called `.probot.yml` in your repository.
+Behaviors are configured in a file called `.probot` in your repository.
 
-```yml
-behaviors:
-  # Auto-respond to new issues and pull requests
-  - on:
-      - issues.opened
-      - pull_request.opened
-    then:
-      comment: "Thanks for your contribution! Expect a reply within 48 hours."
-      label: triage
+```
+# Auto-respond to new issues and pull requests
+on issues.opened and pull_request.opened
+then comment("Thanks for your contribution! Expect a reply within 48 hours.")
+and label(triage);
 
-  # Auto-close new pull requests
-  - on: pull_request.opened
-    then:
-      comment: "Sorry @{{ user.login }}, pull requests are not accepted on this repository."
-      close: true
+# Auto-close new pull requests
+on pull_request.opened
+then comment("Sorry @{{ user.login }}, pull requests are not accepted on this repository.")
+and close;
 ```
 
 ## `behaviors`
@@ -33,24 +28,20 @@ Behaviors are composed of:
 
 Specifies the type of GitHub [webhook event](https://developer.github.com/webhooks/#events) that this behavior applies to:
 
-```yml
-- on: issues
+```
+on issues then…
 ```
 
-Specifying multiple events will trigger this behavior:
+You can also specify multiple events to trigger this behavior:
 
-```yml
-- on:
-  - issues
-  - pull_request
+```
+on issues and pull_request then…
 ```
 
 Many events also have an `action` (e.g. `created` for the `issue` event), which can be referenced with dot notation:
 
-```yml
-- on:
-  - issues.labeled
-  - issues.unlabeled
+```
+on issues.labeled and issues.unlabeled then…
 ```
 
 [Webhook events](https://developer.github.com/webhooks/#events) include:
@@ -84,7 +75,7 @@ TODO: document actions
 
 Only preform the actions if theses conditions are met.
 
-_Heads up! There are not any `when` conditions implemented yet. _
+_Heads up! There are not any `when` conditions implemented yet._
 
 ### `then`
 
@@ -92,86 +83,74 @@ _Heads up! There are not any `when` conditions implemented yet. _
 
 Comments can be posted in response to any event performed on an Issue or Pull Request. Comments use [mustache](https://mustache.github.io/) for templates and can use any data from the event payload.
 
-```yml
-  then:
-    comment: >
-      Hey @{{ user.login }}, thanks for the contribution!
+```
+… then comment("Hey @{{ user.login }}, thanks for the contribution!");
 ```
 
 #### `close`
 
 Close an issue or pull request.
 
-```yml
-  then:
-    close: true
+```
+… then close;
 ```
 
 #### `open`
 
 Reopen an issue or pull request.
 
-```yml
-  then:
-    open: true
+```
+… then open;
 ```
 
 #### `lock`
 
 Lock conversation on an issue or pull request.
 
-```yml
-  then:
-    lock: true
+```
+… then lock;
 ```
 
 #### `unlock`
 
 Unlock conversation on an issue or pull request.
 
-```yml
-  then:
-    unlock: true
+```
+… then unlock;
 ```
 
 #### `label`
 
 Add labels
 
-```yml
-  then:
-    label: bug
+```
+… then label(bug);
 ```
 
 #### `unlabel`
 
 Add labels
 
-```yml
-  then:
-    unlabel: needs-work
-    label: waiting-for-review
+```
+… then unlabel("needs-work") and label("waiting-for-review");
 ```
 
 #### `assign`
 
-```yml
-  then:
-    assign: hubot
+```
+… then assign(hubot);
 ```
 
 #### `unassign`
 
-```yml
-  then:
-    unassign: defunkt
+```
+… then unassign(defunkt);
 ```
 
 #### `react`
 
-```yml
-  then:
-    react: heart # or +1, -1, laugh, confused, heart, hooray
+```
+… then react(heart); # or +1, -1, laugh, confused, heart, hooray
 ```
 
 ---
diff --git a/docs/examples.md b/docs/examples.md
index bc50bf16..6b69c48e 100644
--- a/docs/examples.md
+++ b/docs/examples.md
@@ -5,97 +5,57 @@ _**Heads up!** these examples include configuration options that are aspirationa
 Here are some examples of interesting things you can do by combining these components.
 
 ```yml
-behaviors:
-  # Post welcome message for new contributors
-  - on:
-      - issues.opened
-      - pull_request.opened
-    when:
-      first_time_contributor: true # plugins could implement conditions like this
-    then:
-      comment:
-        from_file: .github/NEW_CONTRIBUTOR_TEMPLATE.md
+# Post welcome message for new contributors
+on issues.opened and pull_request.opened
+when first_time_contributor # plugins could implement conditions like this
+then comment(file(".github/NEW_CONTRIBUTOR_TEMPLATE.md"));
 
-  # Auto-close new pull requests
-  - on:
-      - pull_request.opened
-    then:
-      comment: "Sorry @{{ user.login }}, pull requests are not accepted on this repository."
-      close: true
+# Auto-close new pull requests
+on pull_request.opened
+then comment("Sorry @{{ user.login }}, pull requests are not accepted on this repository.")
+and close;
 
-  # Close issues with no body
-  - on:
-      - issues.opened
-    when:
-      payload:
-        body:
-          matches: /^$/
-    then:
-      comment: "Hey @{{ user.login }}, you didn't include a description of the problem, so we're closing this issue."
+# Close issues with no body
+on issues.opened
+when payload.body matches /^$/
+then comment("Hey @{{ user.login }}, you didn't include a description of the problem, so we're closing this issue.");
 
-  # @mention watchers when label added
-  - on: *.labeled
-    then:
-      comment:
-        # TODO: figure out syntax for loading watchers from file
-        message: "Hey {{ mentions }}, you wanted to know when the `{{ payload.label.name }}` label was added."
+# @mention watchers when label added
+on *.labeled then
+# TODO: figure out syntax for loading watchers from file
+comment("Hey {{ mentions }}, you wanted to know when the `{{ payload.label.name }}` label was added.");
 
-  # Assign a reviewer for new bugs
-  - on: pull_request.labeled
-  - when:
-      - labeled: bug
-    then:
-      - assign:
-          random:
-            from_file: OWNERS
+# Assign a reviewer for new bugs
+on pull_request.labeled
+when labeled(bug)
+then assign(random(file(OWNERS)));
 
-  # Perform actions based on content of comments
-  - on: issue_comment.opened
-    when:
-      payload:
-        issue.body:
-          matches: /^@probot assign @(\w+)$/
-    then:
-      assign: {{ matches[0] }}
-  - on: issue_comment.opened
-    when:
-      payload:
-        issue.body:
-          matches: /^@probot label @(\w+)$/
-    then:
-      label: {{ matches[0] }}
+# Perform actions based on content of comments
+on issue_comment.opened
+when payloadissue.body matches /^@probot assign @(\w+)$/
+then assign({{ matches[0] }})
 
-  # Close stale issues and pull requests
-  - on: *.labeled
-    when:
-      label: needs-work
-      state: open
-    then:
-      delay:
-        after: 7 days
-        close: true
+on issue_comment.opened
+when payload.issue.body matches /^@probot label @(\w+)$/
+then label({{ matches[0] }})
 
-  # Tweet when a new release is created
-  - on: release.published
-    then:
-      tweet: "Get it while it's hot! {{ repository.name }} {{ release.name }} was just released! {{ release.html_url }}"
+# Close stale issues and pull requests
+on *.labeled
+when labeled("needs-work") and state("open")
+then delay(7 days) and close
 
-  # Assign a reviewer issues or pull requests with a label
-  - on:
-      - issues.opened
-      - pull_request.opened
-      - issues.labeled
-      - pull_request.labeled
-    when:
-      label: security
-    then:
-      assign:
-        random:
-          from_team: security-first-responders
+# Tweet when a new release is created
+on release.published
+then tweet("Get it while it's hot! {{ repository.name }} {{ release.name }} was just released! {{ release.html_url }}")
 
-  # Label state transitions
-  # TODO
+# Assign a reviewer issues or pull requests with a label
+on issues.opened and pull_request.opened and issues.labeled and pull_request.labeled
+when labeled(security)
+then assign(random(members(security-first-responders));
 
-  # Apply label based on changed files
-  # TODO
+# Label state transitions
+# TODO
+
+# Apply label based on changed files
+# TODO
 ```
diff --git a/lib/actions/assign.js b/lib/actions/assign.js
index 74d09c4f..6c9cc60c 100644
--- a/lib/actions/assign.js
+++ b/lib/actions/assign.js
@@ -1,12 +1,11 @@
 // Assign one or more users to an issue or pull request.
 //
-// ```yml
-// - then:
-//     # Assign a single user
-//     assign: bkeeepers
+// ```
+// # Assign a single user
+// then assign(bkeepers);
 //
-//     # Assign multiple users
-//     assign: [bkeeepers, benbalter]
+// # Assign multiple users
+// then assign(bkeepers, benbalter);
 // ```
 //
 
diff --git a/lib/actions/unassign.js b/lib/actions/unassign.js
index b262dd1f..42a27252 100644
--- a/lib/actions/unassign.js
+++ b/lib/actions/unassign.js
@@ -1,12 +1,11 @@
 // Unassign one or more users from an issue or pull request.
 //
-// ```yml
-// - then:
-//     # Unassign a single user
-//     unassign: bkeeepers
+// ```
+// # Unassign a single user
+// then unassign(bkeepers);
 //
-//     # Unassign multiple users
-//     unassign: [bkeeepers, benbalter]
+// # Unassign multiple users
+// then unassign(bkeepers, benbalter);
 // ```
 //