diff --git a/docs/notes/development.md b/docs/notes/development.md
index 34d941a..0f4e336 100644
--- a/docs/notes/development.md
+++ b/docs/notes/development.md
@@ -27,6 +27,6 @@ _Ensure you have Node.js v6+ and Yarn installed._
 7. Push the commits from your clone to the fork
 8. From your fork, start a new pull request
 
-It's also a good idea to check out the [gulpfile.js](https://github.com/pegjs/pegjs/blob/master/gulpfile.js) that defines various tasks that are commented with a description of each task.
+It's also a good idea to check out the [package.json](https://github.com/pegjs/pegjs/blob/master/package.json) that defines various scripts.
 
 To see the list of contributors check out the [repository's contributors page](https://github.com/pegjs/pegjs/graphs/contributors).
diff --git a/tools/benchmark/README.md b/tools/benchmark/README.md
index b7e0f19..a3a69f9 100644
--- a/tools/benchmark/README.md
+++ b/tools/benchmark/README.md
@@ -3,5 +3,5 @@ This directory contains the benchmark suite that measures the speed of parsers g
 From the root of the repository:
 
 ```sh
-yarn benchmark
+npx benchmark
 ```
diff --git a/tools/bundle/README.md b/tools/bundle/README.md
new file mode 100644
index 0000000..33946e2
--- /dev/null
+++ b/tools/bundle/README.md
@@ -0,0 +1 @@
+This directory contains a package bundler for PEG.js that is actually a thin layer around [Rollup](https://rollupjs.org/).
diff --git a/tools/impact/README.md b/tools/impact/README.md
index 14ffc69..de43d9e 100644
--- a/tools/impact/README.md
+++ b/tools/impact/README.md
@@ -3,6 +3,6 @@ This directory contains a tool used on the PEG.js repository that measures the i
 From the root of the repository:
 
 ```sh
-yarn impact <commit>
-yarn impact <commit_before> <commit_after>
+npx impact <commit>
+npx impact <commit_before> <commit_after>
 ```