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+# Variables
+
+## Variables keys
+
+All variable keys must contains only letters, digits and '\_'. They must also be no longer than 255 characters.
+
+## List project variables
+
+Get list of variables of a project.
+
+```
+GET /projects/:id/variables
+```
+
+Parameters:
+
+- `id` (required) - The ID of a project
+
+```json
+[
+    {
+        "key": "TEST_VARIABLE_1",
+        "value": "TEST_1"
+    },
+    {
+        "key": "TEST_VARIABLE_2",
+        "value": "TEST_2"
+    }
+]
+```
+
+## Show variable details
+
+Get details of specifica variable of a project.
+
+```
+GET /projects/:id/variables/:key
+```
+
+Parameters:
+
+- `id` (required) - The ID of a project
+- `key` (required) - The `key` of variable
+
+```json
+{
+    "key": "TEST_VARIABLE_1",
+    "value": "TEST_1"
+}
+```
+
+## Create variable
+
+Create new variable in project.
+
+```
+POST /projects/:id/variables
+```
+
+Parameters:
+
+- `id` (required) - The ID of a project
+- `key` (required) - The `key` for variable
+- `value` (required) - The `value` for variable
+
+```json
+{
+    "key": "NEW_VARIABLE",
+    "value": "new value"
+}
+```
+
+## Update variable
+
+Update variable.
+
+```
+PUT /projects/:id/variables/:key
+```
+
+Parameters:
+
+- `id` (required) - The ID of a project
+- `key` (required) - The `key` for variable
+- `value` (required) - The `value` for variable
+
+```json
+{
+    "key": "NEW_VARIABLE",
+    "value": "updated value"
+}
+```
+
+## Remove variable
+
+Remove variable.
+
+```
+DELETE /projects/:id/variables/:key
+```
+
+Parameters:
+
+- `id` (required) - The ID of a project
+- `key` (required) - The `key` for variable
+