diff --git a/gcs/README.md b/gcs/README.md
index b69f52b0..18811e37 100644
--- a/gcs/README.md
+++ b/gcs/README.md
@@ -1,9 +1,52 @@
 gcs
-==========
+===
 
-[![GoDoc](https://godoc.org/github.com/decred/dcrd/gcs?status.png)](https://godoc.org/github.com/decred/dcrd/gcs)
+[![Build Status](https://github.com/decred/dcrd/workflows/Build%20and%20Test/badge.svg)](https://github.com/decred/dcrd/actions)
+[![ISC License](https://img.shields.io/badge/license-ISC-blue.svg)](http://copyfree.org)
+[![GoDoc](https://img.shields.io/badge/godoc-reference-blue.svg)](https://godoc.org/github.com/decred/dcrd/gcs)
 
-Package gcs provides an API for building and using a Golomb-coded set filter
-similar to that described [here](https://giovanni.bajo.it/post/47119962313/golomb-coded-sets-smaller-than-bloom-filters).
+Package gcs provides an API for building and using Golomb-coded sets.
+
+A Golomb-Coded Set (GCS) is a space-efficient probabilistic data structure that
+is used to test set membership with a tunable false positive rate while
+simultaneously preventing false negatives.  In other words, items that are in
+the set will always match, but items that are not in the set will also sometimes
+match with the chosen false positive rate.
+
+This package currently implements two different versions for backwards
+compatibility.  Version 1 is deprecated and therefore should no longer be used.
+
+Version 2 is the GCS variation that follows the specification details in
+[DCP0005](https://github.com/decred/dcps/blob/master/dcp-0005/dcp-0005.mediawiki#golomb-coded-sets).
+
+Version 2 sets do not permit empty items (data of zero length) to be added and
+are parameterized by the following:
+
+* A parameter `B` that defines the remainder code bit size
+* A parameter `M` that defines the false positive rate as `1/M`
+* A key for the SipHash-2-4 function
+* The items to include in the set
 
 A comprehensive suite of tests is provided to ensure proper functionality.
+
+## GCS use in Decred
+
+GCS is used as a mechanism for storing, transmitting, and committing to
+per-block filters.  Consensus-validating full nodes commit to a single filter
+for every block and serve the filter to SPV clients that match against the
+filter locally to determine if the block is potentially relevant.  The required
+parameters for Decred are defined by the blockcf2 package.
+
+For more details, see the [Block Filters section of
+DCP0005](https://github.com/decred/dcps/blob/master/dcp-0005/dcp-0005.mediawiki#block-filters).
+
+## Installation and Updating
+
+```bash
+$ go get -u github.com/decred/dcrd/gcs
+```
+
+## License
+
+Package blockchain is licensed under the [copyfree](http://copyfree.org) ISC
+License.
diff --git a/gcs/doc.go b/gcs/doc.go
index c316380c..5d96c248 100644
--- a/gcs/doc.go
+++ b/gcs/doc.go
@@ -1,26 +1,48 @@
-// Copyright (c) 2016-2017 The btcsuite developers
-// Copyright (c) 2016-2017 The Lightning Network Developers
-// Copyright (c) 2018 The Decred developers
+// Copyright (c) 2018-2019 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
 /*
 Package gcs provides an API for building and using a Golomb-coded set filter.
 
-Golomb-Coded Set
+A Golomb-Coded Set (GCS) is a space-efficient probabilistic data structure that
+is used to test set membership with a tunable false positive rate while
+simultaneously preventing false negatives.  In other words, items that are in
+the set will always match, but items that are not in the set will also sometimes
+match with the chosen false positive rate.
 
-A Golomb-coded set is a probabilistic data structure used similarly to a Bloom
-filter.  A filter uses constant-size overhead plus on average n+2 bits per item
-added to the filter, where 2^-n is the desired false positive (collision)
-probability.
+This package currently implements two different versions for backwards
+compatibility.  Version 1 is deprecated and therefore should no longer be used.
+
+Version 2 is the GCS variation that follows the specification details in
+DCP0005: https://github.com/decred/dcps/blob/master/dcp-0005/dcp-0005.mediawiki#golomb-coded-sets.
+
+Version 2 sets do not permit empty items (data of zero length) to be added and
+are parameterized by the following:
+
+* A parameter `B` that defines the remainder code bit size
+* A parameter `M` that defines the false positive rate as `1/M`
+* A key for the SipHash-2-4 function
+* The items to include in the set
+
+Errors
+
+Errors returned by this package are of type gcs.Error.  This allows the caller
+to programmatically determine the specific error by examining the ErrorCode
+field of the type asserted gcs.Error while still providing rich error messages
+with contextual information.  A convenience function named IsErrorCode is also
+provided to allow callers to easily check for a specific error code.  See
+ErrorCode in the package documentation for a full list.
 
 GCS use in Decred
 
-GCS filters are a mechanism for storing and transmitting per-block filters.  The
-usage is intended to be the inverse of Bloom filters: a consensus-validating
-full node commits to a single filter for every block and serves the filter to
-SPV clients that match against the filter locally to determine if the block is
-potentially relevant.  The suggested collision probability for Decred use is
-2^-20.
+GCS is used as a mechanism for storing, transmitting, and committing to
+per-block filters.  Consensus-validating full nodes commit to a single filter
+for every block and serve the filter to SPV clients that match against the
+filter locally to determine if the block is potentially relevant.  The required
+parameters for Decred are defined by the blockcf2 package.
+
+For more details, see the the Block Filters section of DCP0005:
+https://github.com/decred/dcps/blob/master/dcp-0005/dcp-0005.mediawiki#block-filters
 */
 package gcs