diff --git a/README.md b/README.md
index 0133f94a3..2645b79cd 100644
--- a/README.md
+++ b/README.md
@@ -53,6 +53,75 @@ Place an empty `<trix-editor></trix-editor>` tag on the page. Trix will automati
 
 Like an HTML `<textarea>`, `<trix-editor>` accepts `autofocus` and `placeholder` attributes. Unlike a `<textarea>`, `<trix-editor>` automatically expands vertically to fit its contents.
 
+## Creating a Toolbar
+
+Trix automatically will create a toolbar for you and attach it right before the `<trix-editor>` element. If you'd like to place the toolbar in a different place you can use the `toolbar` attribute:
+
+```html
+<main>
+  <trix-toolbar id="my_toolbar"></trix-toolbar>
+  <div class="more-stuff-inbetween"></div>
+  <trix-editor toolbar="my_toolbar" input="my_input"></trix-editor>
+</main>
+```
+
+To change the toolbar without modifying Trix, you can overwrite the `Trix.config.toolbar.getDefaultHTML()` function. The default toolbar HTML is in `config/toolbar.js`. Trix uses data attributes to determine how to respond to a toolbar button click.
+
+**Toggle Attribute**
+
+With `data-trix-attribute="<attribute name>"`, you can add an attribute to the current selection.
+For example, to apply bold styling to the selected text the button is:
+
+``` html
+<button type="button" class="bold" data-trix-attribute="bold" data-trix-key="b"></button>
+```
+
+Trix will determine that a range of text is selected and will apply the formatting defined in `Trix.config.textAttributes` (found in `config/text_attributes.js`).
+
+`data-trix-key="b"` tells Trix that this attribute should be applied when you use <kbd>meta</kbd>+<kbd>b</kdb>
+
+If the attribute is defined in `Trix.config.blockAttributes`, Trix will apply the attribute to the current block of text.
+
+``` html
+<button type="button" class="quote" data-trix-attribute="quote"></button>
+```
+
+Clicking the quote button toggles whether the block should be rendered with `<blockquote>`.
+
+## Invoking Internal Trix Actions
+
+Internal actions are defined in `controllers/editor_controller.js` and consist of:
+
+* undo
+* redo
+* link
+* increaseBlockLevel
+* decreaseBlockLevel
+
+``` html
+<button type="button" class="block-level decrease" data-trix-action="decreaseBlockLevel"></button>
+```
+
+## Invoking External Custom Actions
+
+If you want to add a button to the toolbar and have it invoke an external action, you can prefix your action name with `x-`. For example, if I want to print a log statement any time my new button is clicked, I would set by button's data attribute to be `data-trix-action="x-log"`
+
+``` html
+<button id="log-button" type="button" data-trix-action="x-log"></button>
+```
+
+To respond to the action, listen for `trix-action-invoke`. The event's `target` property returns a reference to the `<trix-editor>` element, its `invokingElement` property returns a reference to the `<button>` element, and its `actionName` property returns the value of the `[data-trix-action]` attribute. Use the value of the `actionName` property to detect which external action was invoked.
+
+```javascript
+document.addEventListener("trix-action-invoke", function(event) {
+  const { target, invokingElement, actionName } = event
+
+  if (actionName === "x-log") {
+    console.log(`Custom ${actionName} invoked from ${invokingElement.id} button on ${target.id} trix-editor`)
+  }
+})
+```
+
 ## Integrating With Forms
 
 To submit the contents of a `<trix-editor>` with a form, first define a hidden input field in the form and assign it an `id`. Then reference that `id` in the editor’s `input` attribute.
@@ -371,6 +440,8 @@ The `<trix-editor>` element emits several events which you can use to observe an
 
 * `trix-attachment-remove` fires when an attachment is removed from the document. You can access the Trix attachment object through the `attachment` property on the event. You may wish to use this event to clean up remotely stored files.
 
+* `trix-action-invoke` fires when a Trix action is invoked. You can access the `<trix-editor>` element through the event's `target` property, the element responsible for invoking the action through the `invokingElement` property, and the action's name through the `actionName` property. The `trix-action-invoke` event will only fire for [custom](#invoking-external-custom-actions) actions and not for [built-in](#invoking-internal-trix-actions).
+
 # Contributing to Trix
 
 Trix is open-source software, freely distributable under the terms of an [MIT-style license](LICENSE). The [source code is hosted on GitHub](https://github.com/basecamp/trix).
diff --git a/src/test/system/custom_element_test.js b/src/test/system/custom_element_test.js
index 2e77e3fc4..00b2f2250 100644
--- a/src/test/system/custom_element_test.js
+++ b/src/test/system/custom_element_test.js
@@ -133,6 +133,30 @@ testGroup("Custom element API", { template: "editor_empty" }, () => {
     assert.equal(eventCount, 5)
   })
 
+  test("invoking internal actions does not dispatch a trix-action-invoke event", async () => {
+    let event = null
+
+    addEventListener("trix-action-invoke", (ev) => event = ev, { once: true })
+    await clickToolbarButton({ action: "link" })
+
+    assert.equal(null, event)
+  })
+
+  test("invoking external actions dispatches a trix-action-invoke event", async () => {
+    let event = null
+    const editor = getEditorElement()
+    editor.toolbarElement.insertAdjacentHTML("beforeend", `
+      <button id="test-action" type="button" data-trix-action="x-test"></button>
+    `)
+
+    addEventListener("trix-action-invoke", (ev) => event = ev, { once: true })
+    await clickToolbarButton({ action: "x-test" })
+
+    assert.equal(editor, event.target)
+    assert.equal("x-test", event.actionName)
+    assert.equal(document.getElementById("test-action"), event.invokingElement)
+  })
+
   test("element triggers trix-change event after toggling attributes", async () => {
     const element = getEditorElement()
     const { editor } = element