diff --git a/README.md b/README.md
index 1789c59c9..2728b2631 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,12 @@ ARC is a transaction processor for Bitcoin that keeps track of the life cycle of
 Settings for ARC are defined in a configuration file. The default configuration file is `config.yaml` in the root directory. Each setting is documented in the file itself.
 If you want to load `config.yaml` from a different location, you can specify it on the command line using the `-config=<path>` flag.
 
+Each setting in the file `config.yaml` can be overridden with an environment variable. The environment variable needs to have this prefix `ARC_`. A sub setting will be separated using an underscore character. For example the following config setting could be overridden by the environment variable `ARC_METAMORPH_LISTENADDR`
+```yaml
+metamorph:
+  listenAddr:
+```
+
 ## Microservices
 
 To run all the microservices in one process (during development), use the `main.go` file in the root directory.
diff --git a/api/arc.go b/api/arc.go
index ae3bfd2e4..2037f24a9 100644
--- a/api/arc.go
+++ b/api/arc.go
@@ -376,7 +376,7 @@ type POSTTransactionParams struct {
 	// XSkipTxValidation Whether we should skip overall tx validation or not.
 	XSkipTxValidation *SkipTxValidation `json:"X-SkipTxValidation,omitempty"`
 
-	// XCallbackToken Access token for notification callback endpoint.
+	// XCallbackToken Access token for notification callback endpoint. It will be used as a Authorization header for the http callback
 	XCallbackToken *CallbackToken `json:"X-CallbackToken,omitempty"`
 
 	// XMerkleProof Whether to include merkle proofs in the callbacks (true | false).
@@ -406,7 +406,7 @@ type POSTTransactionsParams struct {
 	// XSkipTxValidation Whether we should skip overall tx validation or not.
 	XSkipTxValidation *SkipTxValidation `json:"X-SkipTxValidation,omitempty"`
 
-	// XCallbackToken Access token for notification callback endpoint.
+	// XCallbackToken Access token for notification callback endpoint. It will be used as a Authorization header for the http callback
 	XCallbackToken *CallbackToken `json:"X-CallbackToken,omitempty"`
 
 	// XMerkleProof Whether to include merkle proofs in the callbacks (true | false).
@@ -1847,64 +1847,64 @@ func RegisterHandlersWithBaseURL(router EchoRouter, si ServerInterface, baseURL
 // Base64 encoded, gzipped, json marshaled Swagger object
 var swaggerSpec = []string{
 
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 }
 
 // GetSwagger returns the content of the embedded swagger specification file
diff --git a/api/arc.json b/api/arc.json
index 0b36a5d43..b554291c4 100644
--- a/api/arc.json
+++ b/api/arc.json
@@ -1035,7 +1035,7 @@
       "callbackToken": {
         "name": "X-CallbackToken",
         "in": "header",
-        "description": "Access token for notification callback endpoint.",
+        "description": "Access token for notification callback endpoint. It will be used as a Authorization header for the http callback",
         "schema": {
           "type": "string"
         }
diff --git a/api/arc.yml b/api/arc.yml
index 70cd5811b..547c6d303 100644
--- a/api/arc.yml
+++ b/api/arc.yml
@@ -6,7 +6,7 @@ info:
     name: Open BSV Licence
     url: https://bitcoinassociation.net/open-bsv-license/
 servers:
-- url: https://tapi.taal.com/arc
+  - url: https://tapi.taal.com/arc
 paths:
 
   # Get Policy
@@ -206,7 +206,7 @@ paths:
                 added:
                   summary: Success
                   value:
-                   [
+                    [
                       {
                         "blockHash": "",
                         "blockHeight": 0,
@@ -223,7 +223,7 @@ paths:
                 error:
                   summary: "Invalid outputs"
                   value:
-                   [
+                    [
                       {
                         "detail": "Transaction is invalid because the outputs are non-existent or invalid",
                         "extraInfo": "arc error 463: arc error 463: transaction output 0 satoshis is invalid",
@@ -731,7 +731,7 @@ components:
     callbackToken:
       name: X-CallbackToken
       in: header
-      description: Access token for notification callback endpoint.
+      description: Access token for notification callback endpoint. It will be used as a Authorization header for the http callback
       schema:
         type: string
     merkleProof:
@@ -748,6 +748,6 @@ components:
         type: integer
 
 security:
-  - BearerAuth: []
-  - Api-Key: []
-  - Authorization: []
+  - BearerAuth: [ ]
+  - Api-Key: [ ]
+  - Authorization: [ ]
diff --git a/doc/api.md b/doc/api.md
index 65a2c8629..fab86d736 100644
--- a/doc/api.md
+++ b/doc/api.md
@@ -537,7 +537,7 @@ This endpoint is used to send a raw transaction to a miner for inclusion in the
 |X-SkipFeeValidation|header|boolean|false|Whether we should skip fee validation or not.|
 |X-SkipScriptValidation|header|boolean|false|Whether we should skip script validation or not.|
 |X-SkipTxValidation|header|boolean|false|Whether we should skip overall tx validation or not.|
-|X-CallbackToken|header|string|false|Access token for notification callback endpoint.|
+|X-CallbackToken|header|string|false|Access token for notification callback endpoint. It will be used as a Authorization header for the http callback|
 |X-MerkleProof|header|string|false|Whether to include merkle proofs in the callbacks (true | false).|
 |X-WaitForStatus|header|integer|false|Which status to wait for from the server before returning (2 = RECEIVED, 3 = STORED, 4 = ANNOUNCED_TO_NETWORK, 5 = REQUESTED_BY_NETWORK, 6 = SENT_TO_NETWORK, 7 = ACCEPTED_BY_NETWORK, 8 = SEEN_ON_NETWORK)|
 |body|body|string|true|Transaction hex string|
@@ -800,7 +800,7 @@ This endpoint is used to send multiple raw transactions to a miner for inclusion
 |X-SkipFeeValidation|header|boolean|false|Whether we should skip fee validation or not.|
 |X-SkipScriptValidation|header|boolean|false|Whether we should skip script validation or not.|
 |X-SkipTxValidation|header|boolean|false|Whether we should skip overall tx validation or not.|
-|X-CallbackToken|header|string|false|Access token for notification callback endpoint.|
+|X-CallbackToken|header|string|false|Access token for notification callback endpoint. It will be used as a Authorization header for the http callback|
 |X-MerkleProof|header|string|false|Whether to include merkle proofs in the callbacks (true | false).|
 |X-WaitForStatus|header|integer|false|Which status to wait for from the server before returning (2 = RECEIVED, 3 = STORED, 4 = ANNOUNCED_TO_NETWORK, 5 = REQUESTED_BY_NETWORK, 6 = SENT_TO_NETWORK, 7 = ACCEPTED_BY_NETWORK, 8 = SEEN_ON_NETWORK)|
 |body|body|string|false|none|
@@ -1673,4 +1673,3 @@ and
 |instance|string¦null|false|none|(Optional) Link to actual error on server|
 |txid|string¦null|false|none|Transaction ID this error is referring to|
 |extraInfo|string¦null|false|none|Optional extra information about the error from the miner|
-
diff --git a/doc/arc.json b/doc/arc.json
index 0b36a5d43..b554291c4 100644
--- a/doc/arc.json
+++ b/doc/arc.json
@@ -1035,7 +1035,7 @@
       "callbackToken": {
         "name": "X-CallbackToken",
         "in": "header",
-        "description": "Access token for notification callback endpoint.",
+        "description": "Access token for notification callback endpoint. It will be used as a Authorization header for the http callback",
         "schema": {
           "type": "string"
         }