diff --git a/cmd/genbotcert/README.md b/cmd/genbotcert/README.md
new file mode 100644
index 000000000..2d25f01ba
--- /dev/null
+++ b/cmd/genbotcert/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/cmd/genbotcert.svg)](https://pkg.go.dev/golang.org/x/build/cmd/genbotcert)
+
+# golang.org/x/build/cmd/genbotcert
+
+Command genbotcert generates a private key and CSR for a LUCI bot.
diff --git a/cmd/watchflakes/internal/cache/README.md b/cmd/watchflakes/internal/cache/README.md
new file mode 100644
index 000000000..d584a59ba
--- /dev/null
+++ b/cmd/watchflakes/internal/cache/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/cmd/watchflakes/internal/cache.svg)](https://pkg.go.dev/golang.org/x/build/cmd/watchflakes/internal/cache)
+
+# golang.org/x/build/cmd/watchflakes/internal/cache
+
+Package cache implements a simple file-based cache.
diff --git a/cmd/watchflakes/internal/script/README.md b/cmd/watchflakes/internal/script/README.md
new file mode 100644
index 000000000..9f1d58be8
--- /dev/null
+++ b/cmd/watchflakes/internal/script/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/cmd/watchflakes/internal/script.svg)](https://pkg.go.dev/golang.org/x/build/cmd/watchflakes/internal/script)
+
+# golang.org/x/build/cmd/watchflakes/internal/script
+
+Package script implements a simple classification scripting language.
diff --git a/internal/basedir/README.md b/internal/basedir/README.md
new file mode 100644
index 000000000..0d84e34de
--- /dev/null
+++ b/internal/basedir/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/internal/basedir.svg)](https://pkg.go.dev/golang.org/x/build/internal/basedir)
+
+# golang.org/x/build/internal/basedir
+
+Package basedir finds templates and static files associated with a binary.
diff --git a/internal/dash/README.md b/internal/dash/README.md
new file mode 100644
index 000000000..343e66339
--- /dev/null
+++ b/internal/dash/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/internal/dash.svg)](https://pkg.go.dev/golang.org/x/build/internal/dash)
+
+# golang.org/x/build/internal/dash
+
+Package dash reads build.golang.org's dashboards.
diff --git a/internal/gcsfs/README.md b/internal/gcsfs/README.md
new file mode 100644
index 000000000..f31db3c52
--- /dev/null
+++ b/internal/gcsfs/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/internal/gcsfs.svg)](https://pkg.go.dev/golang.org/x/build/internal/gcsfs)
+
+# golang.org/x/build/internal/gcsfs
+
+gcsfs implements io/fs for GCS, adding writability.
diff --git a/internal/influx/README.md b/internal/influx/README.md
new file mode 100644
index 000000000..0bb5e7a54
--- /dev/null
+++ b/internal/influx/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/internal/influx.svg)](https://pkg.go.dev/golang.org/x/build/internal/influx)
+
+# golang.org/x/build/internal/influx
+
+Package influx provides common constants for setting up and access the performance monitoring InfluxDB instance.
diff --git a/internal/logparser/README.md b/internal/logparser/README.md
new file mode 100644
index 000000000..a36b69572
--- /dev/null
+++ b/internal/logparser/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/internal/logparser.svg)](https://pkg.go.dev/golang.org/x/build/internal/logparser)
+
+# golang.org/x/build/internal/logparser
+
+Package logparser parses build.golang.org dashboard logs.
diff --git a/internal/relui/sign/README.md b/internal/relui/sign/README.md
new file mode 100644
index 000000000..112ea7697
--- /dev/null
+++ b/internal/relui/sign/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/internal/relui/sign.svg)](https://pkg.go.dev/golang.org/x/build/internal/relui/sign)
+
+# golang.org/x/build/internal/relui/sign
+
+Package sign provides implementations for servers which can sign Go release artifacts.
diff --git a/perf/app/README.md b/perf/app/README.md
new file mode 100644
index 000000000..7f085cff8
--- /dev/null
+++ b/perf/app/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perf/app.svg)](https://pkg.go.dev/golang.org/x/build/perf/app)
+
+# golang.org/x/build/perf/app
+
+Package app implements the performance data analysis server.
diff --git a/perfdata/README.md b/perfdata/README.md
new file mode 100644
index 000000000..417860362
--- /dev/null
+++ b/perfdata/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perfdata.svg)](https://pkg.go.dev/golang.org/x/build/perfdata)
+
+# golang.org/x/build/perfdata
+
+Package perfdata contains a client for the performance data storage server.
diff --git a/perfdata/app/README.md b/perfdata/app/README.md
new file mode 100644
index 000000000..c0f095a1f
--- /dev/null
+++ b/perfdata/app/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perfdata/app.svg)](https://pkg.go.dev/golang.org/x/build/perfdata/app)
+
+# golang.org/x/build/perfdata/app
+
+Package app implements the performance data storage server.
diff --git a/perfdata/db/README.md b/perfdata/db/README.md
new file mode 100644
index 000000000..5b6ab3d68
--- /dev/null
+++ b/perfdata/db/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perfdata/db.svg)](https://pkg.go.dev/golang.org/x/build/perfdata/db)
+
+# golang.org/x/build/perfdata/db
+
+Package db provides the high-level database interface for the storage app.
diff --git a/perfdata/db/sqlite3/README.md b/perfdata/db/sqlite3/README.md
new file mode 100644
index 000000000..4d04e81f8
--- /dev/null
+++ b/perfdata/db/sqlite3/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perfdata/db/sqlite3.svg)](https://pkg.go.dev/golang.org/x/build/perfdata/db/sqlite3)
+
+# golang.org/x/build/perfdata/db/sqlite3
+
+Package sqlite3 provides the sqlite3 driver for x/build/perfdata/db.
diff --git a/perfdata/fs/README.md b/perfdata/fs/README.md
new file mode 100644
index 000000000..d53a7dd0f
--- /dev/null
+++ b/perfdata/fs/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perfdata/fs.svg)](https://pkg.go.dev/golang.org/x/build/perfdata/fs)
+
+# golang.org/x/build/perfdata/fs
+
+Package fs provides a backend-agnostic filesystem layer for storing performance results.
diff --git a/perfdata/fs/gcs/README.md b/perfdata/fs/gcs/README.md
new file mode 100644
index 000000000..72f15b942
--- /dev/null
+++ b/perfdata/fs/gcs/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perfdata/fs/gcs.svg)](https://pkg.go.dev/golang.org/x/build/perfdata/fs/gcs)
+
+# golang.org/x/build/perfdata/fs/gcs
+
+Package gcs implements the fs.FS interface using Google Cloud Storage.
diff --git a/perfdata/fs/local/README.md b/perfdata/fs/local/README.md
new file mode 100644
index 000000000..86a2c3da5
--- /dev/null
+++ b/perfdata/fs/local/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perfdata/fs/local.svg)](https://pkg.go.dev/golang.org/x/build/perfdata/fs/local)
+
+# golang.org/x/build/perfdata/fs/local
+
+Package local implements the fs.FS interface using local files.
diff --git a/perfdata/localperfdata/README.md b/perfdata/localperfdata/README.md
new file mode 100644
index 000000000..084d6e690
--- /dev/null
+++ b/perfdata/localperfdata/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perfdata/localperfdata.svg)](https://pkg.go.dev/golang.org/x/build/perfdata/localperfdata)
+
+# golang.org/x/build/perfdata/localperfdata
+
+Localperfdata runs an HTTP server for benchmark perfdata.
diff --git a/perfdata/query/README.md b/perfdata/query/README.md
new file mode 100644
index 000000000..103168249
--- /dev/null
+++ b/perfdata/query/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/perfdata/query.svg)](https://pkg.go.dev/golang.org/x/build/perfdata/query)
+
+# golang.org/x/build/perfdata/query
+
+Package query provides tools for parsing a query.
diff --git a/third_party/bandchart/README.md b/third_party/bandchart/README.md
new file mode 100644
index 000000000..8d7378d98
--- /dev/null
+++ b/third_party/bandchart/README.md
@@ -0,0 +1,7 @@
+<!-- Auto-generated by x/build/update-readmes.go -->
+
+[![Go Reference](https://pkg.go.dev/badge/golang.org/x/build/third_party/bandchart.svg)](https://pkg.go.dev/golang.org/x/build/third_party/bandchart)
+
+# golang.org/x/build/third_party/bandchart
+
+Package bandchart provides an embedded bandchart.js.