diff --git a/api/error.defaults.go b/api/error.defaults.go
index 583126f..4a1e9e6 100644
--- a/api/error.defaults.go
+++ b/api/error.defaults.go
@@ -3,129 +3,82 @@ package api
 import "net/http"
 
 var (
-	// ErrorUnknown represents any error which cause is unknown.
+	// ErrUnknown represents any error which cause is unknown.
 	// It might also be used for debug purposes as this error
 	// has to be used the less possible
-	ErrorUnknown Error = -1
+	ErrUnknown = Err{-1, "unknown error", http.StatusOK}
 
-	// ErrorSuccess represents a generic successful service execution
-	ErrorSuccess Error = 0
+	// ErrSuccess represents a generic successful service execution
+	ErrSuccess = Err{0, "all right", http.StatusOK}
 
-	// ErrorFailure is the most generic error
-	ErrorFailure Error = 1
+	// ErrFailure is the most generic error
+	ErrFailure = Err{1, "it failed", http.StatusInternalServerError}
 
-	// ErrorNoMatchFound has to be set when trying to fetch data and there is no result
-	ErrorNoMatchFound Error = 2
+	// ErrNoMatchFound is set when trying to fetch data and there is no result
+	ErrNoMatchFound = Err{2, "resource not found", http.StatusOK}
 
-	// ErrorAlreadyExists has to be set when trying to insert data, but identifiers or
+	// ErrAlreadyExists is set when trying to insert data, but identifiers or
 	// unique fields already exists
-	ErrorAlreadyExists Error = 3
+	ErrAlreadyExists = Err{3, "already exists", http.StatusOK}
 
-	// ErrorCreation has to be set when there is a creation/insert error
-	ErrorCreation Error = 4
+	// ErrCreation is set when there is a creation/insert error
+	ErrCreation = Err{4, "create error", http.StatusOK}
 
-	// ErrorModification has to be set when there is an update/modification error
-	ErrorModification Error = 5
+	// ErrModification is set when there is an update/modification error
+	ErrModification = Err{5, "update error", http.StatusOK}
 
-	// ErrorDeletion has to be set when there is a deletion/removal error
-	ErrorDeletion Error = 6
+	// ErrDeletion is set when there is a deletion/removal error
+	ErrDeletion = Err{6, "delete error", http.StatusOK}
 
-	// ErrorTransaction has to be set when there is a transactional error
-	ErrorTransaction Error = 7
+	// ErrTransaction is set when there is a transactional error
+	ErrTransaction = Err{7, "transactional error", http.StatusOK}
 
-	// ErrorUpload has to be set when a file upload failed
-	ErrorUpload Error = 100
+	// ErrUpload is set when a file upload failed
+	ErrUpload = Err{100, "upload failed", http.StatusInternalServerError}
 
-	// ErrorDownload has to be set when a file download failed
-	ErrorDownload Error = 101
+	// ErrDownload is set when a file download failed
+	ErrDownload = Err{101, "download failed", http.StatusInternalServerError}
 
-	// MissingDownloadHeaders has to be set when the implementation
+	// MissingDownloadHeaders is set when the implementation
 	// of a service of type 'download' (which returns a file instead of
 	// a set or output fields) is missing its HEADER field
-	MissingDownloadHeaders Error = 102
+	MissingDownloadHeaders = Err{102, "download headers are missing", http.StatusBadRequest}
 
-	// ErrorMissingDownloadBody has to be set when the implementation
+	// ErrMissingDownloadBody is set when the implementation
 	// of a service of type 'download' (which returns a file instead of
 	// a set or output fields) is missing its BODY field
-	ErrorMissingDownloadBody Error = 103
+	ErrMissingDownloadBody = Err{103, "download body is missing", http.StatusBadRequest}
 
-	// ErrorUnknownService is set when there is no service matching
+	// ErrUnknownService is set when there is no service matching
 	// the http request URI.
-	ErrorUnknownService Error = 200
+	ErrUnknownService = Err{200, "unknown service", http.StatusServiceUnavailable}
 
-	// ErrorUncallableService is set when there the requested service's
+	// ErrUncallableService is set when there the requested service's
 	// implementation (plugin file) is not found/callable
-	ErrorUncallableService Error = 202
+	ErrUncallableService = Err{202, "uncallable service", http.StatusServiceUnavailable}
 
-	// ErrorNotImplemented is set when a handler is not implemented yet
-	ErrorNotImplemented Error = 203
+	// ErrNotImplemented is set when a handler is not implemented yet
+	ErrNotImplemented = Err{203, "not implemented", http.StatusNotImplemented}
 
-	// ErrorPermission is set when there is a permission error by default
+	// ErrPermission is set when there is a permission error by default
 	// the api returns a permission error when the current scope (built
 	// by middlewares) does not match the scope required in the config.
 	// You can add your own permission policy and use this error
-	ErrorPermission Error = 300
+	ErrPermission = Err{300, "permission error", http.StatusUnauthorized}
 
-	// ErrorToken has to be set (usually in authentication middleware) to tell
+	// ErrToken is set (usually in authentication middleware) to tell
 	// the user that this authentication token is expired or invalid
-	ErrorToken Error = 301
+	ErrToken = Err{301, "token error", http.StatusForbidden}
 
-	// ErrorMissingParam is set when a *required* parameter is missing from the
+	// ErrMissingParam is set when a *required* parameter is missing from the
 	// http request
-	ErrorMissingParam Error = 400
+	ErrMissingParam = Err{400, "missing parameter", http.StatusBadRequest}
 
-	// ErrorInvalidParam is set when a given parameter fails its type check as
+	// ErrInvalidParam is set when a given parameter fails its type check as
 	// defined in the config file.
-	ErrorInvalidParam Error = 401
+	ErrInvalidParam = Err{401, "invalid parameter", http.StatusBadRequest}
 
-	// ErrorInvalidDefaultParam is set when an optional parameter's default value
+	// ErrInvalidDefaultParam is set when an optional parameter's default value
 	// does not match its type.
-	ErrorInvalidDefaultParam Error = 402
+	ErrInvalidDefaultParam = Err{402, "invalid default param", http.StatusBadRequest}
 )
-
-var errorReasons = map[Error]string{
-	ErrorUnknown:             "unknown error",
-	ErrorSuccess:             "all right",
-	ErrorFailure:             "it failed",
-	ErrorNoMatchFound:        "resource not found",
-	ErrorAlreadyExists:       "already exists",
-	ErrorCreation:            "create error",
-	ErrorModification:        "update error",
-	ErrorDeletion:            "delete error",
-	ErrorTransaction:         "transactional error",
-	ErrorUpload:              "upload failed",
-	ErrorDownload:            "download failed",
-	MissingDownloadHeaders:   "download headers are missing",
-	ErrorMissingDownloadBody: "download body is missing",
-	ErrorUnknownService:      "unknown service",
-	ErrorUncallableService:   "uncallable service",
-	ErrorNotImplemented:      "not implemented",
-	ErrorPermission:          "permission error",
-	ErrorToken:               "token error",
-	ErrorMissingParam:        "missing parameter",
-	ErrorInvalidParam:        "invalid parameter",
-	ErrorInvalidDefaultParam: "invalid default param",
-}
-var errorStatus = map[Error]int{
-	ErrorUnknown:             http.StatusOK,
-	ErrorSuccess:             http.StatusOK,
-	ErrorFailure:             http.StatusInternalServerError,
-	ErrorNoMatchFound:        http.StatusOK,
-	ErrorAlreadyExists:       http.StatusOK,
-	ErrorCreation:            http.StatusOK,
-	ErrorModification:        http.StatusOK,
-	ErrorDeletion:            http.StatusOK,
-	ErrorTransaction:         http.StatusOK,
-	ErrorUpload:              http.StatusInternalServerError,
-	ErrorDownload:            http.StatusInternalServerError,
-	MissingDownloadHeaders:   http.StatusBadRequest,
-	ErrorMissingDownloadBody: http.StatusBadRequest,
-	ErrorUnknownService:      http.StatusServiceUnavailable,
-	ErrorUncallableService:   http.StatusServiceUnavailable,
-	ErrorNotImplemented:      http.StatusNotImplemented,
-	ErrorPermission:          http.StatusUnauthorized,
-	ErrorToken:               http.StatusForbidden,
-	ErrorMissingParam:        http.StatusBadRequest,
-	ErrorInvalidParam:        http.StatusBadRequest,
-	ErrorInvalidDefaultParam: http.StatusBadRequest,
-}
diff --git a/api/error.go b/api/error.go
index 52f97f7..36d8800 100644
--- a/api/error.go
+++ b/api/error.go
@@ -1,49 +1,21 @@
 package api
 
 import (
-	"encoding/json"
 	"fmt"
-	"net/http"
 )
 
-// Error represents an http response error following the api format.
+// Err represents an http response error following the api format.
 // These are used by the services to set the *execution status*
 // directly into the response as JSON alongside response output fields.
-type Error int
-
-func (e Error) Error() string {
-	reason, ok := errorReasons[e]
-	if !ok {
-		return ErrorUnknown.Error()
-	}
-	return fmt.Sprintf("[%d] %s", e, reason)
+type Err struct {
+	// error code (unique)
+	Code int `json:"code"`
+	// error small description
+	Reason string `json:"reason"`
+	// associated HTTP status
+	Status int
 }
 
-// Status returns the associated HTTP status code
-func (e Error) Status() int {
-	status, ok := errorStatus[e]
-	if !ok {
-		return http.StatusOK
-	}
-	return status
-}
-
-// MarshalJSON implements encoding/json.Marshaler interface
-func (e Error) MarshalJSON() ([]byte, error) {
-	// use unknown error if no reason
-	reason, ok := errorReasons[e]
-	if !ok {
-		return ErrorUnknown.MarshalJSON()
-	}
-
-	// format to proper struct
-	formatted := struct {
-		Code   int    `json:"code"`
-		Reason string `json:"reason"`
-	}{
-		Code:   int(e),
-		Reason: reason,
-	}
-
-	return json.Marshal(formatted)
+func (e Err) Error() string {
+	return fmt.Sprintf("[%d] %s", e.Code, e.Reason)
 }
diff --git a/api/response.go b/api/response.go
index a7ce08c..ae403f8 100644
--- a/api/response.go
+++ b/api/response.go
@@ -13,7 +13,7 @@ type Response struct {
 	Data    ResponseData
 	Status  int
 	Headers http.Header
-	err     Error
+	err     Err
 }
 
 // EmptyResponse creates an empty response.
@@ -21,13 +21,13 @@ func EmptyResponse() *Response {
 	return &Response{
 		Status:  http.StatusOK,
 		Data:    make(ResponseData),
-		err:     ErrorFailure,
+		err:     ErrFailure,
 		Headers: make(http.Header),
 	}
 }
 
 // WithError sets the error
-func (res *Response) WithError(err Error) *Response {
+func (res *Response) WithError(err Err) *Response {
 	res.err = err
 	return res
 }
@@ -53,7 +53,7 @@ func (res *Response) MarshalJSON() ([]byte, error) {
 }
 
 func (res *Response) ServeHTTP(w http.ResponseWriter, r *http.Request) error {
-	w.WriteHeader(res.err.Status())
+	w.WriteHeader(res.err.Status)
 	encoded, err := json.Marshal(res)
 	if err != nil {
 		return err
diff --git a/internal/dynfunc/errors.go b/internal/dynfunc/errors.go
index 0d2a4b2..ca87692 100644
--- a/internal/dynfunc/errors.go
+++ b/internal/dynfunc/errors.go
@@ -23,7 +23,7 @@ const errUnexpectedInput = cerr("unexpected input struct")
 const errMissingHandlerOutput = cerr("handler must have at least 1 output")
 
 // errMissingHandlerOutputError - missing error output for handler
-const errMissingHandlerOutputError = cerr("handler must have its last output of type api.Error")
+const errMissingHandlerOutputError = cerr("handler must have its last output of type api.Err")
 
 // errMissingRequestArgument - missing request argument for handler
 const errMissingRequestArgument = cerr("handler first argument must be of type api.Request")
@@ -47,4 +47,4 @@ const errMissingOutputFromConfig = cerr("missing a parameter from configuration"
 const errWrongParamTypeFromConfig = cerr("invalid struct field type")
 
 // errMissingHandlerErrorOutput - missing handler output error
-const errMissingHandlerErrorOutput = cerr("last output must be of type api.Error")
+const errMissingHandlerErrorOutput = cerr("last output must be of type api.Err")
diff --git a/internal/dynfunc/handler.go b/internal/dynfunc/handler.go
index f932a89..c12069c 100644
--- a/internal/dynfunc/handler.go
+++ b/internal/dynfunc/handler.go
@@ -16,7 +16,7 @@ type Handler struct {
 
 // Build a handler from a service configuration and a dynamic function
 //
-// @fn must have as a signature : `func(inputStruct) (*outputStruct, api.Error)`
+// @fn must have as a signature : `func(inputStruct) (*outputStruct, api.Err)`
 //  - `inputStruct` is a struct{} containing a field for each service input (with valid reflect.Type)
 //  - `outputStruct` is a struct{} containing a field for each service output (with valid reflect.Type)
 //
@@ -46,8 +46,9 @@ func Build(fn interface{}, service config.Service) (*Handler, error) {
 }
 
 // Handle binds input @data into the dynamic function and returns map output
-func (h *Handler) Handle(data map[string]interface{}) (map[string]interface{}, api.Error) {
-	fnv := reflect.ValueOf(h.fn)
+func (h *Handler) Handle(data map[string]interface{}) (map[string]interface{}, api.Err) {
+	var ert = reflect.TypeOf(api.Err{})
+	var fnv = reflect.ValueOf(h.fn)
 
 	callArgs := []reflect.Value{}
 
@@ -80,7 +81,12 @@ func (h *Handler) Handle(data map[string]interface{}) (map[string]interface{}, a
 	// no output OR pointer to output struct is nil
 	outdata := make(map[string]interface{})
 	if len(h.spec.Output) < 1 || output[0].IsNil() {
-		return outdata, api.Error(output[len(output)-1].Int())
+		var structerr = output[len(output)-1].Convert(ert)
+		return outdata, api.Err{
+			Code:   int(structerr.FieldByName("Code").Int()),
+			Reason: structerr.FieldByName("Reason").String(),
+			Status: int(structerr.FieldByName("Status").Int()),
+		}
 	}
 
 	// extract struct from pointer
@@ -91,6 +97,11 @@ func (h *Handler) Handle(data map[string]interface{}) (map[string]interface{}, a
 		outdata[name] = field.Interface()
 	}
 
-	// extract api.Error
-	return outdata, api.Error(output[len(output)-1].Int())
+	// extract api.Err
+	var structerr = output[len(output)-1].Convert(ert)
+	return outdata, api.Err{
+		Code:   int(structerr.FieldByName("Code").Int()),
+		Reason: structerr.FieldByName("Reason").String(),
+		Status: int(structerr.FieldByName("Status").Int()),
+	}
 }
diff --git a/internal/dynfunc/spec.go b/internal/dynfunc/spec.go
index 2449a85..571c9ae 100644
--- a/internal/dynfunc/spec.go
+++ b/internal/dynfunc/spec.go
@@ -91,9 +91,9 @@ func (s spec) checkOutput(fnv reflect.Value) error {
 		return errMissingHandlerOutput
 	}
 
-	// last output must be api.Error
+	// last output must be api.Err
 	errOutput := fnt.Out(fnt.NumOut() - 1)
-	if !errOutput.AssignableTo(reflect.TypeOf(api.ErrorUnknown)) {
+	if !errOutput.AssignableTo(reflect.TypeOf(api.ErrUnknown)) {
 		return errMissingHandlerErrorOutput
 	}
 
diff --git a/internal/dynfunc/spec_test.go b/internal/dynfunc/spec_test.go
index a9ad5e9..b8599bc 100644
--- a/internal/dynfunc/spec_test.go
+++ b/internal/dynfunc/spec_test.go
@@ -111,28 +111,28 @@ func TestOutputCheck(t *testing.T) {
 		Fn     interface{}
 		Err    error
 	}{
-		// no input -> missing api.Error
+		// no input -> missing api.Err
 		{
 			Output: map[string]reflect.Type{},
 			Fn:     func() {},
 			Err:    errMissingHandlerOutput,
 		},
-		// no input -> with last type not api.Error
+		// no input -> with last type not api.Err
 		{
 			Output: map[string]reflect.Type{},
 			Fn:     func() bool { return true },
 			Err:    errMissingHandlerErrorOutput,
 		},
-		// no input -> with api.Error
+		// no input -> with api.Err
 		{
 			Output: map[string]reflect.Type{},
-			Fn:     func() api.Error { return api.ErrorSuccess },
+			Fn:     func() api.Err { return api.ErrSuccess },
 			Err:    nil,
 		},
 		// func can have output if not specified
 		{
 			Output: map[string]reflect.Type{},
-			Fn:     func() (*struct{}, api.Error) { return nil, api.ErrorSuccess },
+			Fn:     func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			Err:    nil,
 		},
 		// missing output struct in func
@@ -140,7 +140,7 @@ func TestOutputCheck(t *testing.T) {
 			Output: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:  func() api.Error { return api.ErrorSuccess },
+			Fn:  func() api.Err { return api.ErrSuccess },
 			Err: errMissingParamOutput,
 		},
 		// output not a pointer
@@ -148,7 +148,7 @@ func TestOutputCheck(t *testing.T) {
 			Output: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:  func() (int, api.Error) { return 0, api.ErrorSuccess },
+			Fn:  func() (int, api.Err) { return 0, api.ErrSuccess },
 			Err: errMissingParamOutput,
 		},
 		// output not a pointer to struct
@@ -156,7 +156,7 @@ func TestOutputCheck(t *testing.T) {
 			Output: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:  func() (*int, api.Error) { return nil, api.ErrorSuccess },
+			Fn:  func() (*int, api.Err) { return nil, api.ErrSuccess },
 			Err: errMissingParamOutput,
 		},
 		// unexported param name
@@ -164,7 +164,7 @@ func TestOutputCheck(t *testing.T) {
 			Output: map[string]reflect.Type{
 				"test1": reflect.TypeOf(int(0)),
 			},
-			Fn:  func() (*struct{}, api.Error) { return nil, api.ErrorSuccess },
+			Fn:  func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			Err: errUnexportedName,
 		},
 		// output field missing
@@ -172,7 +172,7 @@ func TestOutputCheck(t *testing.T) {
 			Output: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:  func() (*struct{}, api.Error) { return nil, api.ErrorSuccess },
+			Fn:  func() (*struct{}, api.Err) { return nil, api.ErrSuccess },
 			Err: errMissingParamFromConfig,
 		},
 		// output field invalid type
@@ -180,7 +180,7 @@ func TestOutputCheck(t *testing.T) {
 			Output: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:  func() (*struct{ Test1 string }, api.Error) { return nil, api.ErrorSuccess },
+			Fn:  func() (*struct{ Test1 string }, api.Err) { return nil, api.ErrSuccess },
 			Err: errWrongParamTypeFromConfig,
 		},
 		// output field valid type
@@ -188,7 +188,7 @@ func TestOutputCheck(t *testing.T) {
 			Output: map[string]reflect.Type{
 				"Test1": reflect.TypeOf(int(0)),
 			},
-			Fn:  func() (*struct{ Test1 int }, api.Error) { return nil, api.ErrorSuccess },
+			Fn:  func() (*struct{ Test1 int }, api.Err) { return nil, api.ErrSuccess },
 			Err: nil,
 		},
 		// ignore type check on nil type
@@ -196,7 +196,7 @@ func TestOutputCheck(t *testing.T) {
 			Output: map[string]reflect.Type{
 				"Test1": nil,
 			},
-			Fn:  func() (*struct{ Test1 int }, api.Error) { return nil, api.ErrorSuccess },
+			Fn:  func() (*struct{ Test1 int }, api.Err) { return nil, api.ErrSuccess },
 			Err: nil,
 		},
 	}
diff --git a/server.go b/server.go
index dbc2074..2a81e41 100644
--- a/server.go
+++ b/server.go
@@ -18,14 +18,14 @@ func (server Server) ServeHTTP(res http.ResponseWriter, req *http.Request) {
 	// 1. find a matching service in the config
 	service := server.conf.Find(req)
 	if service == nil {
-		errorHandler(api.ErrorUnknownService).ServeHTTP(res, req)
+		handleError(api.ErrUnknownService, w, r)
 		return
 	}
 
 	// 2. extract request data
 	dataset, err := extractRequestData(service, *req)
 	if err != nil {
-		errorHandler(api.ErrorMissingParam).ServeHTTP(res, req)
+		handleError(api.ErrMissingParam, w, r)
 		return
 	}
 
@@ -39,7 +39,7 @@ func (server Server) ServeHTTP(res http.ResponseWriter, req *http.Request) {
 
 	// 4. fail if found no handler
 	if handler == nil {
-		errorHandler(api.ErrorUncallableService).ServeHTTP(res, req)
+		handleError(api.ErrUncallableService, w, r)
 		return
 	}
 
@@ -69,29 +69,27 @@ func (server Server) ServeHTTP(res http.ResponseWriter, req *http.Request) {
 	response.ServeHTTP(res, req)
 }
 
-func errorHandler(err api.Error) http.HandlerFunc {
-	return func(res http.ResponseWriter, req *http.Request) {
-		r := api.EmptyResponse().WithError(err)
-		r.ServeHTTP(res, req)
-	}
+func handleError(err api.Err, w http.ResponseWriter, r *http.Request) {
+	var response = api.EmptyResponse().WithError(err)
+	response.ServeHTTP(w, r)
 }
 
 func extractRequestData(service *config.Service, req http.Request) (*reqdata.T, error) {
-	dataset := reqdata.New(service)
+	var dataset = reqdata.New(service)
 
-	// 3. extract URI data
-	err := dataset.GetURI(req)
+	// URI data
+	var err = dataset.GetURI(req)
 	if err != nil {
 		return nil, err
 	}
 
-	// 4. extract query data
+	// query data
 	err = dataset.GetQuery(req)
 	if err != nil {
 		return nil, err
 	}
 
-	// 5. extract form/json data
+	// form/json data
 	err = dataset.GetForm(req)
 	if err != nil {
 		return nil, err