diff --git a/README.md b/README.md
index 3f08801..b6030a5 100644
--- a/README.md
+++ b/README.md
@@ -55,16 +55,26 @@ Configuration syntax is YAML and has to be done in following order:
 
 Right now there is only the configuration parameter for hooks, here
 each hook has to be configured, It contains following fields:
-- command: String for a command to be executed when all filters
-  match. Pointers ([RFC 6901](https://tools.ietf.org/html/rfc6901)) to
-  JSON fields may be used to be replaced with data from the JSON data
-  with `{{ /field/pointed/to }}`. Further `{{ event }}` and `{{
-  signature }}` are valid variables as they contain the values from
-  the regarding header fields of the http request.
+- command: A command to be executed if a filter matches
 - signature: Name of the HTTP header field containing the signature.
 - secrets: List of secrets.
 - filters: List of filters.
 
+### Command
+To pass data to a command following two different methods can be used.
+
+#### JSON Pointers
+Use JSON pointers ([RFC 6901](https://tools.ietf.org/html/rfc6901))
+point to values of a JSON field from the JSON data.
+
+Example: `{{ /field/pointed/to }}`.
+
+#### Header
+Use values from header fields sent with the HTTP request.
+
+Example: `{{ header X-Gitea-Event }}`.
+
+### Filter
 Each filter must have following fields:
 - pointer: pointer to the JSON field according to [RFC
   6901](https://tools.ietf.org/html/rfc6901)
diff --git a/src/main.rs b/src/main.rs
index 309745e..b264a7f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -67,21 +67,29 @@ fn replace_parameter(input: &str, headers: &HeaderMap, data: &serde_json::Value)
     let parse: IResult<&str, Vec<&str>> = many0(alt((
         map_res(
             delimited(tag("{{"), take_until("}}"), tag("}}")),
-            |param: &str| match param.trim() {
-                "event" => {
-                    if let Some(event) = headers.get_one("X-Gitea-Event") {
-                        Ok(event)
-                    } else {
-                        bail!("Could not extract event parameter from header");
+            |param: &str| {
+                let expr = param.trim().split(' ').collect::<Vec<&str>>();
+
+                match expr.get(0) {
+                    Some(&"header") => {
+                        if let Some(field) = expr.get(1) {
+                            match headers.get_one(field) {
+                                Some(value) => Ok(value),
+                                _ => bail!("Could not extract event parameter from header"),
+                            }
+                        } else {
+                            bail!("Missing parameter for `header` expression");
+                        }
                     }
-                }
-                pointer => match data.pointer(pointer) {
-                    Some(value) => match value.as_str() {
-                        Some(value) => Ok(value),
-                        _ => bail!("Could not convert value `{}` to string", value),
+                    Some(pointer) => match data.pointer(pointer) {
+                        Some(value) => match value.as_str() {
+                            Some(value) => Ok(value),
+                            _ => bail!("Could not convert value `{}` to string", value),
+                        },
+                        _ => bail!("Could not convert field `{}` to string", param.trim()),
                     },
-                    _ => bail!("Could not convert field `{}` to string", param.trim()),
-                },
+                    None => bail!("Missing expression in `{}`", input),
+                }
             },
         ),
         take_until("{{"),
@@ -297,7 +305,7 @@ fn get_config() -> Result<File> {
         return Ok(config);
     }
 
-    bail!("No configuration files found.");
+    bail!("No configuration file found.");
 }
 
 fn main() -> Result<()> {
@@ -471,7 +479,7 @@ mod tests {
 
         assert_eq!(
             replace_parameter(
-                "   {{ event }}   command",
+                "   {{ header X-Gitea-Event }}   command",
                 &map,
                 &json!({ "field1": { "foo": "bar" } })
             )