diff --git a/gitbook/configuration/custom-parameters.md b/gitbook/configuration/custom-parameters.md
new file mode 100644
index 00000000..b02aff0e
--- /dev/null
+++ b/gitbook/configuration/custom-parameters.md
@@ -0,0 +1,18 @@
+# Custom Request Parameter
+
+Since version `5.2.0` it is possible to customize the requests send by the agent to the OPs and add custom request
+parameters.
+
+Custom parameters can be configured in a config file named `custom_parameters.config`. As usual the file can be placed
+in `/etc/oidc-agent` or the agent directory. If both are present parameters are merged together.
+
+The `custom_parameters.config` contains a json array of parameter specifications. A parameter specification is a json
+object that can have the following fields:
+
+| Field Name    | Description                                                                                                                                                                                                                                                                                                                                                                                |
+|---------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `parameter`   | The name of the parameter to be added to the request                                                                                                                                                                                                                                                                                                                                       |
+| `value`       | The value that should be used. The value can be given in different ways. If the value starts with a `$` the following characters are interpreted as an environment variable and the value is read from this variable. If the given value starts with an `/` it is interpreted as a file path and the first line from that file is used as the value. Otherwise the value is used directly. |
+| `for_issuer`  | A JSON array of issuer urls for which this parameter should be used                                                                                                                                                                                                                                                                                                                        |
+| `for_account` | A JSON array of account shortnames for which this parameter should be used                                                                                                                                                                                                                                                                                                                 |
+| `request`     | A JSON array of requests for which this parameter should be used. Possible values are `refresh`, `auth_url`, `code-exchange`,`device-init`,`device-polling`,`registration`,`revocation`,`password`                                                                                                                                                                                         |
diff --git a/gitbook/configuration/default-accounts.md b/gitbook/configuration/default-accounts.md
index c47d74c9..8f9d8bfc 100644
--- a/gitbook/configuration/default-accounts.md
+++ b/gitbook/configuration/default-accounts.md
@@ -1,9 +1,6 @@
 ## Default Account Configuration for a Provider
+
 The `issuer.config` file in the [oidc-agent directory](directory.md) can also
-be used to set an default account configuration file for each provider by adding
-the shortname of this account configuration after the issuer url.
-A line in the `issuer.config` file should look the following:
-```
-<issuer_url>[<space><shortname>]
-```
+be used to set a default account configuration file for each provider by using the `default_account` claim. for more
+details please refer to the [documentations about issuer.config](issuers.md).
 
diff --git a/gitbook/provider/known-issues.md b/gitbook/provider/known-issues.md
index b53176ea..2cfcdce3 100644
--- a/gitbook/provider/known-issues.md
+++ b/gitbook/provider/known-issues.md
@@ -1,11 +1,14 @@
 ## Known Issues
+
 ### Expiring Refresh Tokens
+
 oidc-agent assumes that refresh tokens do not expire. But some providers might
 use refresh tokens that expire after a certain time or when they are not used
 for a specific time. To prevent the latter use oidc-agent / oidc-token regularly
-(you also can use a cron job). 
+(you can also use a cron job).
 
 oidc-agent is able to
 update a stored refresh token. However, therefore it has to receive a new
-refresh token from the provider. If a refresh token expired (e.g. because the token was used within the lifetime of that token), use `oidc-gen --reauthenticate <short_name>` to re-authenticate and update the refresh token.
+refresh token from the provider. If a refresh token expired (e.g. because the token was used within the lifetime of that
+token), use `oidc-gen --reauthenticate <short_name>` to re-authenticate and update the refresh token.