diff --git a/book/src/become-a-validator-source.md b/book/src/become-a-validator-source.md
index d0555f0f34..d700ee6968 100644
--- a/book/src/become-a-validator-source.md
+++ b/book/src/become-a-validator-source.md
@@ -3,9 +3,10 @@
 ## 1. Download and install Lighthouse
 
 If you already have Rust installed, you can install Lighthouse with the
-following three commands:
+following commands (don't forget to use the `testnet5` branch):
 
 - `$ git clone https://github.com/sigp/lighthouse.git`
+- `$ git checkout testnet5`
 - `$ cd lighthouse`
 - `$ make`
 
diff --git a/book/src/become-a-validator.md b/book/src/become-a-validator.md
index 11bbf245f8..c86819390f 100644
--- a/book/src/become-a-validator.md
+++ b/book/src/become-a-validator.md
@@ -1,12 +1,4 @@
-# Become an Ethereum 2.0 Validator*
-
-_* Testnet validator_
-
----
-**The lighthouse testnet is currently down. We expect to bring it up again in
-late-January or early-February. Thanks to all who participated in the testnet,
-we look forward to having your input again in the future.**
----
+# Become an Ethereum 2.0 Testnet Validator
 
 Running Lighthouse validator is easy if you're familiar with the terminal. It
 runs on Linux, MacOS and Windows and we have a Docker work-flow.
diff --git a/book/src/http_advanced.md b/book/src/http_advanced.md
index 01e20b4461..822b6ffffd 100644
--- a/book/src/http_advanced.md
+++ b/book/src/http_advanced.md
@@ -1,4 +1,4 @@
-# Lighthouse REST API: `/spec`
+# Lighthouse REST API: `/advanced`
 
 The `/advanced` endpoints provide information Lighthouse specific data structures for advanced debugging.
 
@@ -112,4 +112,4 @@ Typical Responses | 200
     "voluntary_exits": []
 }
 ```
-_Truncated for brevity._
\ No newline at end of file
+_Truncated for brevity._
diff --git a/book/src/http_beacon.md b/book/src/http_beacon.md
index 2ad5e7839f..b08d1969ef 100644
--- a/book/src/http_beacon.md
+++ b/book/src/http_beacon.md
@@ -702,4 +702,4 @@ canonical head state will be used.
 
 ### Returns
 
-The return format is identical to the [`/beacon/validators`](#beaconvalidators) response body.
\ No newline at end of file
+The return format is identical to the [`/beacon/validators`](#beaconvalidators) response body.
diff --git a/book/src/http_validator.md b/book/src/http_validator.md
index 5f91002a61..34c24875bc 100644
--- a/book/src/http_validator.md
+++ b/book/src/http_validator.md
@@ -159,7 +159,12 @@ The return format is identical to the [Validator Duties](#validator-duties) resp
 
 ## `/validator/block`
 
-Produces and returns a `BeaconBlock` object from the current state.
+Produces and returns an unsigned `BeaconBlock` object.
+
+The block will be produced with the given `slot` and the parent block will be the
+highest block in the canonical chain that has a slot less than `slot`. The
+block will still be produced if some other block is also known to be at `slot`
+(i.e., it may produce a block that would be slashable if signed).
 
 ### HTTP Specification
 
@@ -210,6 +215,15 @@ Returns a `BeaconBlock` object.
 
 Produces and returns an unsigned `Attestation` from the current state.
 
+The attestation will reference the `beacon_block_root` of the highest block in
+the canonical chain with a slot equal to or less than the given `slot`.
+
+An error will be returned if the given slot is more than
+`SLOTS_PER_HISTORICAL_VECTOR` slots behind the current head block.
+
+This endpoint is not protected against slashing. Signing the returned
+attestation may result in a slashable offence.
+
 ### HTTP Specification
 
 | Property | Specification |
@@ -255,7 +269,12 @@ Returns a `Attestation` object with a default signature. The `signature` field s
 
 ## `/validator/block`
 
-Publishes a `SignedBeaconBlock` object to the network.
+Accepts a `SignedBeaconBlock` for verification. If it is valid, it will be
+imported into the local database and published on the network. Invalid blocks
+will not be published to the network.
+
+A block may be considered invalid because it is fundamentally incorrect, or its
+parent has not yet been imported.
 
 ### HTTP Specification
 
@@ -318,7 +337,13 @@ Else, returns a processing error description.
 
 ## `/validator/attestation`
 
-Publishes a `Attestation` object to the network.
+Accepts an `Attestation` for verification. If it is valid, it will be imported
+into the local database and published to the network. Invalid attestations will
+not be published to the network.
+
+An attestation may be considered invalid because it is fundamentally incorrect
+or because the beacon node has not imported the relevant blocks required to
+verify it.
 
 ### HTTP Specification
 
@@ -362,4 +387,4 @@ Else, returns a processing error description.
   },
   "signature": "0xb76a1768c18615b5ade91a92e7d2ed0294f7e088e56e30fbe7e3aa6799c443b11bccadd578ca2cbd95d395ab689b9e4d03c88a56641791ab38dfa95dc1f4d24d1b19b9d36c96c20147ad03$649bd3c6c7e8a39cf2ffb99e07b4964d52854559f"
 }
-```
\ No newline at end of file
+```
diff --git a/book/src/websockets.md b/book/src/websockets.md
index f1eb274759..69cf0e18d6 100644
--- a/book/src/websockets.md
+++ b/book/src/websockets.md
@@ -1,5 +1,8 @@
 # Websocket API
 
+**Note: the WebSocket server _only_ emits events. It does not accept any
+requests. Use the [HTTP API](./http.md) for requests.**
+
 By default, a Lighthouse `beacon_node` exposes a websocket server on `localhost:5053`.
 
 The following CLI flags control the websocket server: