diff --git a/Sources/CoreATProtocol/OAuth/ATProtoOAuth.swift b/Sources/CoreATProtocol/OAuth/ATProtoOAuth.swift
index 61982fc..e6726e0 100644
--- a/Sources/CoreATProtocol/OAuth/ATProtoOAuth.swift
+++ b/Sources/CoreATProtocol/OAuth/ATProtoOAuth.swift
@@ -57,7 +57,7 @@ public struct ATProtoAuthStorage: Sendable {
     }
 }
 
-public enum ATProtoOAuthError: Error, Sendable {
+public enum ATProtoOAuthError: LocalizedError, Sendable {
     case invalidConfiguration
     case authenticationFailed(String)
     case identityResolutionFailed
@@ -68,6 +68,31 @@ public enum ATProtoOAuthError: Error, Sendable {
     case malformedAuthorizationCallback
     case tokenRequestFailed(String)
     case invalidTokenResponse
+
+    public var errorDescription: String? {
+        switch self {
+        case .invalidConfiguration:
+            "OAuth configuration is invalid"
+        case .authenticationFailed(let detail):
+            "Authentication failed: \(detail)"
+        case .identityResolutionFailed:
+            "Failed to resolve AT Protocol identity"
+        case .privateKeyExportFailed:
+            "Failed to export DPoP private key"
+        case .missingRequiredScope(let scope):
+            "Missing required scope: \(scope)"
+        case .subjectMismatch(let expected, let actual):
+            "Subject mismatch — expected \(expected), got \(actual)"
+        case .issuerMismatch(let expected, let actual):
+            "Issuer mismatch — expected \(expected), got \(actual)"
+        case .malformedAuthorizationCallback:
+            "Authorization callback URL is malformed"
+        case .tokenRequestFailed(let detail):
+            "Token request failed: \(detail)"
+        case .invalidTokenResponse:
+            "Invalid token response from server"
+        }
+    }
 }
 
 /// Type alias for the user authenticator callback