diff --git a/helm/cron_jobs/README.md b/helm/cron_jobs/README.md
new file mode 100644
index 00000000000..edd63378621
--- /dev/null
+++ b/helm/cron_jobs/README.md
@@ -0,0 +1,18 @@
+Replayer cron jobs
+==================
+
+There are replayer cron jobs for Mainnet, Devnet, and Berkeley. These
+jobs are run daily, to replay a day's worth of transactions.
+
+Each cron job downloads the most recent archive dump corresponding to
+a network, and loads the data into PostgreSQL. That results in an
+archive database. The most recent replayer checkpoint file is
+downloaded, which provides the starting point for the replayer. When
+the replayer runs, it creates new checkpoint files every 50
+blocks. When the replayer finishes, it uploads the most recent
+checkpoint file, so it can be used in the following day's run. If
+there are any errors, the replayer logs are also uploaded.
+
+There is a separate checkpoint file bucket for each network.  Both the
+checkpoint files and error files for a given network are uploaded to
+the same bucket.
diff --git a/src/app/archive_blocks/README.md b/src/app/archive_blocks/README.md
new file mode 100644
index 00000000000..718e7a48467
--- /dev/null
+++ b/src/app/archive_blocks/README.md
@@ -0,0 +1,20 @@
+archive_blocks
+==============
+
+The `archive_blocks` app adds blocks in either "precomputed" or
+"extensional" format to the archive database.
+
+Precomputed blocks are stored in the bucket `mina_network_block_data`
+on Google Cloud Storage. Blocks are named NETWORK-HEIGHT-STATEHASH.json.
+Example: mainnet-100000-3NKLvMCimUjX1zjjiC3XPMT34D1bVQGzkKW58XDwFJgQ5wDQ9Tki.json.
+
+Extensional blocks are extracted from other archive databases using
+the `extract_blocks` app.
+
+As many blocks as are available can be added at a time, but all blocks
+must be in the same format.
+
+Except for blocks from the original mainnet, both precomputed and
+extensional blocks have a version in their JSON representation. That
+version must match the corresponding OCaml type in the code when this
+app was built.
diff --git a/src/app/archive_blocks/archive_blocks.ml b/src/app/archive_blocks/archive_blocks.ml
index caa4203939e..7851ca04518 100644
--- a/src/app/archive_blocks/archive_blocks.ml
+++ b/src/app/archive_blocks/archive_blocks.ml
@@ -1,4 +1,4 @@
-(* archive_blocks.ml -- archive precomputed or extensional blocks to Postgresql *)
+(* archive_blocks.ml *)
 
 open Core_kernel
 open Async
diff --git a/src/app/extract_blocks/README.md b/src/app/extract_blocks/README.md
new file mode 100644
index 00000000000..bbaecdbb29b
--- /dev/null
+++ b/src/app/extract_blocks/README.md
@@ -0,0 +1,12 @@
+extract_blocks
+==============
+
+The `extract_blocks` app pulls out individual blocks from an archive
+database in "extensional" format. Such blocks can be added to other
+archive databases using the `archive_blocks` app.
+
+Blocks are extracted into files with name <state-hash>.json.
+
+The app offers the choice to extract all canonical blocks, or a
+subchain specified with starting state hash, or a subchain specified
+with starting and ending state hashes.
diff --git a/src/app/extract_blocks/extract_blocks.ml b/src/app/extract_blocks/extract_blocks.ml
index f4fa0ac2e77..e7f58718cba 100644
--- a/src/app/extract_blocks/extract_blocks.ml
+++ b/src/app/extract_blocks/extract_blocks.ml
@@ -1,4 +1,5 @@
 (* extract_blocks.ml -- dump extensional blocks from archive db *)
+
 [@@@coverage exclude_file]
 
 open Core_kernel
diff --git a/src/app/missing_blocks_auditor/README.md b/src/app/missing_blocks_auditor/README.md
new file mode 100644
index 00000000000..e5db4ee64a3
--- /dev/null
+++ b/src/app/missing_blocks_auditor/README.md
@@ -0,0 +1,10 @@
+missing_blocks_auditor
+======================
+
+The `missing_blocks_auditor` app looks for blocks without parent
+blocks in an archive database.
+
+The app also looks for blocks marked as pending that are lower (have a
+lesser height) than the highest (most recent) canonical block. There
+can be such blocks if blocks are added when there are missing blocks
+in the database.
diff --git a/src/app/missing_blocks_auditor/missing_blocks_auditor.ml b/src/app/missing_blocks_auditor/missing_blocks_auditor.ml
index 5bce995ea28..e6fd538f1b5 100644
--- a/src/app/missing_blocks_auditor/missing_blocks_auditor.ml
+++ b/src/app/missing_blocks_auditor/missing_blocks_auditor.ml
@@ -1,4 +1,4 @@
-(* missing_blocks_auditor.ml -- report missing blocks from an archive db *)
+(* missing_blocks_auditor.ml *)
 
 open Core_kernel
 open Async