diff --git a/internal/config/private.go b/internal/config/private.go
new file mode 100644
index 0000000..4d517a4
--- /dev/null
+++ b/internal/config/private.go
@@ -0,0 +1,112 @@
+package config
+
+import (
+	"fmt"
+	"strings"
+)
+
+// format checks for format errors and missing required fields
+// it also sets default values to optional fields
+func (c *Controller) format(controllerName string) error {
+
+	/* (1) Check each method
+	---------------------------------------------------------*/
+	methods := []struct {
+		Name string
+		Ptr  *Method
+	}{
+		{"GET", c.GET},
+		{"POST", c.POST},
+		{"PUT", c.PUT},
+		{"DELETE", c.DELETE},
+	}
+
+	for _, method := range methods {
+
+		/* (1) ignore non-defined method */
+		if method.Ptr == nil {
+			continue
+		}
+
+		/* (2) Fail on missing description */
+		if len(method.Ptr.Description) < 1 {
+			return fmt.Errorf("Missing %s.%s description", controllerName, method.Name)
+		}
+
+		/* (3) stop if no parameter */
+		if method.Ptr.Parameters == nil || len(*method.Ptr.Parameters) < 1 {
+			continue
+		}
+
+		/* check parameters */
+		for pName, pData := range *method.Ptr.Parameters {
+
+			/* (4) Fail on invalid rename (set but empty) */
+			if pData.Rename != nil && len(*pData.Rename) < 1 {
+				return fmt.Errorf("Empty rename for %s.%s parameter '%s'", controllerName, method.Name, pName)
+			}
+
+			/* (5) Check for name/rename conflict */
+			for paramName, param := range *method.Ptr.Parameters {
+
+				// ignore self
+				if pName == paramName {
+					continue
+				}
+
+				// 1. Same rename field
+				if pData.Rename != nil && param.Rename != nil && *pData.Rename == *param.Rename {
+					return fmt.Errorf("Rename conflict for %s.%s parameter '%s'", controllerName, method.Name, *pData.Rename)
+				}
+
+				// 2. Not-renamed field matches a renamed field
+				if pData.Rename == nil && param.Rename != nil && pName == *param.Rename {
+					return fmt.Errorf("Name conflict for %s.%s parameter '%s'", controllerName, method.Name, pName)
+				}
+
+				// 3. Renamed field matches name
+				if pData.Rename != nil && param.Rename == nil && *pData.Rename == paramName {
+					return fmt.Errorf("Name conflict for %s.%s parameter '%s'", controllerName, method.Name, pName)
+				}
+
+			}
+
+			/* (6) Fail on missing description */
+			if len(pData.Description) < 1 {
+				return fmt.Errorf("Missing description for %s.%s parameter '%s'", controllerName, method.Name, pName)
+			}
+
+			/* (7) Fail on missing type */
+			if len(pData.Type) < 1 {
+				return fmt.Errorf("Missing type for %s.%s parameter '%s'", controllerName, method.Name, pName)
+			}
+		}
+
+	}
+
+	/* (2) Check child controllers
+	---------------------------------------------------------*/
+	/* (1) Stop if no child */
+	if c.Children == nil || len(c.Children) < 1 {
+		return nil
+	}
+
+	/* (2) For each controller */
+	for ctlName, ctl := range c.Children {
+
+		/* (3) Invalid name */
+		if strings.Contains(ctlName, "/") {
+			return fmt.Errorf("Controller '%s' must not contain any slash '/'", ctlName)
+		}
+
+		/* (4) Check recursively */
+		err := ctl.format(ctlName)
+		if err != nil {
+			return err
+		}
+
+	}
+
+	return nil
+
+}
diff --git a/internal/config/public.go b/internal/config/public.go
index 27c8d4f..dc4ba37 100644
--- a/internal/config/public.go
+++ b/internal/config/public.go
@@ -29,6 +29,12 @@ func Load(path string) (*Controller, error) {
 		return nil, err
 	}
 
+	/* (4) Format result */
+	err = receiver.format("/")
+	if err != nil {
+		return nil, err
+	}
+
 	return receiver, nil
 
 }