diff --git a/Readme.md b/Readme.md
new file mode 100644
index 0000000..c577136
--- /dev/null
+++ b/Readme.md
@@ -0,0 +1,63 @@
+# webextension-rpc
+
+This module provides a *Remote Procedure Call* abstraction around the message passing that is
+available to WebExtension (browser extension) scripts. It makes it easier to call a function in the
+background script from a tab’s content script, or vice versa.
+
+
+## Example use
+
+In `background.js`:
+
+    function myFunc(arg) {
+      return arg * 2
+    }
+    makeRemotelyCallable({ myFunc })
+
+In `content_script.js`:
+
+    const myRemoteFunc = remoteFunction('myFunc')
+    myRemoteFunc(21).then(result => { ... result is 42! ... })
+
+Note that the remote function always returns a `Promise`, which resolves with the remote function’s
+actual return value (if the return value is itself a Promise, its result is awaited too).
+
+
+## Install
+
+### Using NPM
+
+This module is published [on npm](https://www.npmjs.com/package/webextension-rpc).
+
+Run `npm install webextension-rpc` or equivalent.
+
+### Standalone
+
+Try one of the magic npm bundlers, for example:
+
+`wget https://wzrd.in/standalone/webextension-rpc -O webextension-rpc.js`
+
+
+## API
+
+### `remoteFunction(functionName, { tabId })`
+
+Create a proxy function that invokes the specified remote function.
+
+- `functionName` (string, required): name of the function as registered on the remote side.
+- `options` (object, optional):
+    - `tabId` (number): The id of the tab whose content script is the remote side. Leave undefined
+      to call the background script (from a content script).
+
+### `makeRemotelyCallable(functions, { insertExtraArg })`
+
+Register one or more functions to enable remote scripts to call them. Arguments:
+
+- `functions` (object, required): An object with a `{ functionName: function }` mapping. Each
+  function will be remotely callable using the given name.
+- `options` (object, optional):
+    - `insertExtraArg` (boolean, default is `false`): If truthy, each executed function also
+      receives, as its first argument before the arguments it was invoked with, a [Tab][] object,
+      which contains the details of the tab that sent the message.
+
+[Tab]: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/tabs/Tab
diff --git a/src/webextension-rpc.js b/src/webextension-rpc.js
index 01d0cfd..d097854 100644
--- a/src/webextension-rpc.js
+++ b/src/webextension-rpc.js
@@ -1,24 +1,4 @@
 
-// A Remote Procedure Call abstraction around the message passing available to
-// WebExtension scripts. Usable to call a function in the background script from
-// a tab's content script, or vice versa.
-//
-// The calling side always gets a Promise of the return value. The executing
-// (remote) function can be an async function (= it returns a Promise), whose
-// completion then will then be waited for.
-
-// Example use:
-//
-// === background.js ===
-// function myFunc(arg) {
-// 	return arg*2
-// }
-// makeRemotelyCallable({myFunc})
-//
-// === content_script.js ===
-// const myRemoteFunc = remoteFunction('myFunc')
-// myRemoteFunc(21).then(result => { ... result is 42! ... })
-
 // Our secret tokens to recognise our messages
 const RPC_CALL = '__RPC_CALL__'
 const RPC_RESPONSE = '__RPC_RESPONSE__'
@@ -37,15 +17,9 @@ export class RemoteError extends Error {
 	}
 }
 
+
 // === Initiating side ===
 
-// Create a proxy function that invokes the specified remote function.
-// Arguments
-// - funcName (required): name of the function as registered on the remote side.
-// - options (optional): {
-//	   tabId: The id of the tab whose content script is the remote side.
-//			  Leave undefined to call the background script (from a tab).
-//   }
 export function remoteFunction(funcName, { tabId } = {}) {
 	const otherSide = (tabId !== undefined)
 		? "the tab's content script"
@@ -145,18 +119,6 @@ function incomingRPCListener(message, sender) {
 // A bit of global state to ensure we only attach the event listener once.
 let enabled = false
 
-// Register a function to allow remote scripts to call it.
-// Arguments:
-// - functions (required):
-//	 An object with a {functionName: function} mapping.
-//	 Each function will be callable with the given name.
-// - options (optional): {
-//	   insertExtraArg:
-//		   If truthy, each executed function also receives, as its first
-//		   argument before the arguments it was invoked with, an object with
-//		   the details of the tab that sent the message.
-//   }
-
 export function makeRemotelyCallable(functions, { insertExtraArg = false } = {}) {
 	// Every function is passed an extra argument with sender information,
 	// so remove this from the call if this was not desired.