diff --git a/api.go b/api.go
index 4c137ec..2e7d385 100644
--- a/api.go
+++ b/api.go
@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"fmt"
 	"log"
 	"net/url"
 	"strconv"
@@ -86,15 +85,15 @@ func NewDerivAPI(endpoint string, appID int, lang, origin string, opts ...APIOpt
 	}
 
 	if urlEnpoint.Scheme != "wss" && urlEnpoint.Scheme != "ws" {
-		return nil, fmt.Errorf("invalid endpoint scheme")
+		return nil, ErrInvalidSchema
 	}
 
 	if appID < 1 {
-		return nil, fmt.Errorf("invalid app id")
+		return nil, ErrInvalidAppID
 	}
 
 	if lang == "" || len(lang) != 2 {
-		return nil, fmt.Errorf("invalid language")
+		return nil, ErrInvalidLanguage
 	}
 
 	query := urlEnpoint.Query()
@@ -357,7 +356,7 @@ func (api *Client) Send(ctx context.Context, reqID int, request any) (chan []byt
 	case <-ctx.Done():
 		return nil, ctx.Err()
 	case <-api.ctx.Done():
-		return nil, fmt.Errorf("connection closed")
+		return nil, ErrConnectionClosed
 	case api.reqChan <- req:
 		return respChan, nil
 	}
@@ -375,13 +374,13 @@ func (api *Client) SendRequest(ctx context.Context, reqID int, request, response
 
 	select {
 	case <-api.ctx.Done():
-		return fmt.Errorf("connection closed")
+		return ErrConnectionClosed
 	case <-ctx.Done():
 		return ctx.Err()
 	case responseJSON, ok := <-respChan:
 		if !ok {
 			api.logDebugf("Connection closed while waiting for response for request %d", reqID)
-			return fmt.Errorf("connection closed")
+			return ErrConnectionClosed
 		}
 
 		if err := parseError(responseJSON); err != nil {
diff --git a/errors.go b/errors.go
index d8d6703..c373af5 100644
--- a/errors.go
+++ b/errors.go
@@ -2,13 +2,22 @@ package deriv
 
 import (
 	"encoding/json"
+	"fmt"
+)
+
+var (
+	ErrConnectionClosed    = fmt.Errorf("connection closed")
+	ErrEmptySubscriptionID = fmt.Errorf("subscription ID is empty")
+	ErrInvalidSchema       = fmt.Errorf("invalid endpoint scheme")
+	ErrInvalidAppID        = fmt.Errorf("invalid app ID")
+	ErrInvalidLanguage     = fmt.Errorf("invalid language")
 )
 
 // APIError represents an error returned by the Deriv API service.
 type APIError struct {
-	Details map[string]interface{} `json:"details"`
-	Code    string                 `json:"code"`
-	Message string                 `json:"message"`
+	Details *json.RawMessage `json:"details"`
+	Code    string           `json:"code"`
+	Message string           `json:"message"`
 }
 
 // Error returns the error message associated with the APIError.
@@ -16,18 +25,27 @@ func (e *APIError) Error() string {
 	return e.Message
 }
 
-// APIErrorResponse represents an error response returned by the Deriv API service.
-type APIErrorResponse struct {
+// ParseDetails parses the details field of the APIError into the provided value.
+func (e *APIError) ParseDetails(v any) error {
+	if e.Details == nil {
+		return nil
+	}
+
+	return json.Unmarshal(*e.Details, v)
+}
+
+// apiErrorResponse represents an error response returned by the Deriv API service.
+type apiErrorResponse struct {
 	// Error is the APIError associated with the response.
 	Error APIError `json:"error"`
 }
 
 // parseError parses a JSON error response from the Deriv API service into an error.
-// If the response is not a valid JSON-encoded APIErrorResponse, an error is returned.
-// If the APIErrorResponse contains a non-empty APIError, it is returned as an error.
+// If the response is not a valid JSON-encoded apiErrorResponse, an error is returned.
+// If the apiErrorResponse contains a non-empty APIError, it is returned as an error.
 // Otherwise, nil is returned.
 func parseError(rawResponse []byte) error {
-	var errorResponse APIErrorResponse
+	var errorResponse apiErrorResponse
 
 	err := json.Unmarshal(rawResponse, &errorResponse)
 	if err != nil {
diff --git a/errors_test.go b/errors_test.go
index 0ad96a3..dcc0a6d 100644
--- a/errors_test.go
+++ b/errors_test.go
@@ -6,11 +6,13 @@ import (
 	"testing"
 )
 
+var expectedDetails json.RawMessage = []byte(`{"TestKey":"TestValue"}`)
+
 func TestAPIError_Error(t *testing.T) {
 	err := &APIError{
 		Code:    "test-code",
 		Message: "test-message",
-		Details: map[string]interface{}{"test-key": "test-value"},
+		Details: &expectedDetails,
 	}
 
 	expected := err.Message
@@ -22,11 +24,11 @@ func TestAPIError_Error(t *testing.T) {
 }
 
 func TestParseError_ValidResponse(t *testing.T) {
-	errorResponse := APIErrorResponse{
+	errorResponse := apiErrorResponse{
 		Error: APIError{
 			Code:    "test-code",
 			Message: "test-message",
-			Details: map[string]interface{}{"test-key": "test-value"},
+			Details: &expectedDetails,
 		},
 	}
 
@@ -65,7 +67,7 @@ func TestParseError_EmptyErrorResponse(t *testing.T) {
 }
 
 func TestParseError_EmptyAPIError(t *testing.T) {
-	errorResponse := APIErrorResponse{
+	errorResponse := apiErrorResponse{
 		Error: APIError{},
 	}
 
@@ -80,3 +82,44 @@ func TestParseError_EmptyAPIError(t *testing.T) {
 		t.Errorf("parseError() returned %v, expected %v", actual, nil)
 	}
 }
+func TestAPIError_ParseDetails_ValidDetails(t *testing.T) {
+	details := struct {
+		TestKey string `json:"TestKey"`
+	}{}
+
+	apiErr := &APIError{
+		Code:    "test-code",
+		Message: "test-message",
+		Details: &expectedDetails,
+	}
+
+	if err := apiErr.ParseDetails(&details); err != nil {
+		t.Errorf("Expected no error, got %v", err)
+	}
+
+	if details.TestKey != "TestValue" {
+		t.Errorf("ParseDetails() did not parse details correctly, expected %q, got %q", "test-value", details.TestKey)
+	}
+}
+
+func TestAPIError_ParseDetails_EmptyDetails(t *testing.T) {
+	details := struct {
+		TestKey string `json:"TestKey"`
+	}{}
+
+	apiErr := &APIError{
+		Code:    "test-code",
+		Message: "test-message",
+		Details: nil,
+	}
+
+	err := apiErr.ParseDetails(&details)
+
+	if err != nil {
+		t.Errorf("Expected no error, got %v", err)
+	}
+
+	if details.TestKey != "" {
+		t.Errorf("ParseDetails() did not handle empty details correctly, expected %q, got %q", "", details.TestKey)
+	}
+}
diff --git a/subscriptions.go b/subscriptions.go
index ab55b11..c513bd9 100644
--- a/subscriptions.go
+++ b/subscriptions.go
@@ -5,7 +5,6 @@ package deriv
 import (
 	"context"
 	"encoding/json"
-	"fmt"
 	"sync"
 
 	"github.com/ksysoev/deriv-api/schema"
@@ -49,7 +48,7 @@ func parseSubsciption(rawResponse []byte) (SubscriptionResponse, error) {
 	}
 
 	if sub.Subscription.ID == "" {
-		return sub, fmt.Errorf("subscription ID is empty")
+		return sub, ErrEmptySubscriptionID
 	}
 
 	return sub, nil
@@ -125,7 +124,7 @@ func (s *Subsciption[initResp, Resp]) Start(reqID int, request any) (initResp, e
 		if !ok {
 			s.API.logDebugf("Connection closed while waiting for response for request %d", reqID)
 
-			return resp, fmt.Errorf("connection closed")
+			return resp, ErrConnectionClosed
 		}
 
 		subResp, err := parseSubsciption(initResponse)
diff --git a/subscriptions_test.go b/subscriptions_test.go
index 89ea0a5..b4c5614 100644
--- a/subscriptions_test.go
+++ b/subscriptions_test.go
@@ -2,8 +2,6 @@ package deriv
 
 import (
 	"context"
-	"errors"
-	"fmt"
 	"reflect"
 	"testing"
 	"time"
@@ -57,15 +55,14 @@ func TestParseSubscription_EmptyInput(t *testing.T) {
 
 func TestParseSubscription_EmptySubscriptionData(t *testing.T) {
 	input := []byte(`{}`)
-	expectedErr := fmt.Errorf("subscription ID is empty")
 
 	_, err := parseSubsciption(input)
 	if err == nil {
 		t.Errorf("Expected an error, but got nil")
 	}
 
-	if errors.Is(err, expectedErr) {
-		t.Errorf("Expected %+v, but got %+v", expectedErr, err)
+	if err != ErrEmptySubscriptionID {
+		t.Errorf("Expected '%+v', but got '%+v'", ErrEmptySubscriptionID, err)
 	}
 }