diff --git a/backend/src/auth/jwt.guard.ts b/backend/src/auth/jwt.guard.ts
index c33f292d..077eddb6 100644
--- a/backend/src/auth/jwt.guard.ts
+++ b/backend/src/auth/jwt.guard.ts
@@ -1,7 +1,13 @@
-import { ExecutionContext, Injectable } from "@nestjs/common";
+import {
+	ExecutionContext,
+	ForbiddenException,
+	Injectable,
+	UnauthorizedException,
+} from "@nestjs/common";
 import { Reflector } from "@nestjs/core";
 import { AuthGuard } from "@nestjs/passport";
 import { IS_PUBLIC_PATH } from "src/utils/decorators/auth.decorator";
+import { AuthorizedUser } from "src/utils/types/req.type";
 
 @Injectable()
 export class JwtAuthGuard extends AuthGuard("jwt") {
@@ -19,4 +25,17 @@ export class JwtAuthGuard extends AuthGuard("jwt") {
 		}
 		return super.canActivate(context);
 	}
+
+	handleRequest<User = AuthorizedUser>(err: Error, user: User, info: Error): User {
+		if (err || !user) {
+			if (info?.name === "TokenExpiredError") {
+				throw new UnauthorizedException("Token has expired.");
+			} else if (info?.name === "JsonWebTokenError") {
+				throw new UnauthorizedException("Invalid token");
+			} else {
+				throw err || new ForbiddenException("Access denied");
+			}
+		}
+		return user;
+	}
 }
diff --git a/backend/src/documents/documents.service.ts b/backend/src/documents/documents.service.ts
index 31d30300..dec88286 100644
--- a/backend/src/documents/documents.service.ts
+++ b/backend/src/documents/documents.service.ts
@@ -43,7 +43,7 @@ export class DocumentsService {
 				},
 			});
 		} catch (e) {
-			throw new NotFoundException();
+			throw new NotFoundException("Document not found");
 		}
 
 		return {
diff --git a/backend/src/files/files.service.ts b/backend/src/files/files.service.ts
index c147bc65..6c378d59 100644
--- a/backend/src/files/files.service.ts
+++ b/backend/src/files/files.service.ts
@@ -46,11 +46,11 @@ export class FilesService {
 				},
 			});
 		} catch (e) {
-			throw new UnauthorizedException();
+			throw new UnauthorizedException("Client unauthorized.");
 		}
 
 		if (contentLength > 10_000_000) {
-			throw new UnprocessableEntityException();
+			throw new UnprocessableEntityException("Content length too long.");
 		}
 
 		const fileKey = `${workspace.slug}-${generateRandomKey()}.${contentType.split("/")[1]}`;
@@ -75,7 +75,7 @@ export class FilesService {
 			});
 			return getSignedUrl(this.s3Client, command, { expiresIn: 3600 });
 		} catch (e) {
-			throw new NotFoundException();
+			throw new NotFoundException("File not found.");
 		}
 	}
 
diff --git a/backend/src/intelligence/intelligence.service.ts b/backend/src/intelligence/intelligence.service.ts
index 44101862..ceb1bfcc 100644
--- a/backend/src/intelligence/intelligence.service.ts
+++ b/backend/src/intelligence/intelligence.service.ts
@@ -25,7 +25,7 @@ export class IntelligenceService {
 		};
 		const selectedPrompt = promptTemplates[feature];
 
-		if (!selectedPrompt) throw new NotFoundException();
+		if (!selectedPrompt) throw new NotFoundException("Feature not found");
 
 		return selectedPrompt;
 	}
diff --git a/backend/src/users/users.service.ts b/backend/src/users/users.service.ts
index 04de8452..edc1fce6 100644
--- a/backend/src/users/users.service.ts
+++ b/backend/src/users/users.service.ts
@@ -74,7 +74,7 @@ export class UsersService {
 		const { conflict } = await this.checkService.checkNameConflict(nickname);
 
 		if (conflict) {
-			throw new ConflictException();
+			throw new ConflictException("The nickname conflicts.");
 		}
 
 		await this.prismaService.user.update({
diff --git a/backend/src/workspace-documents/workspace-documents.service.ts b/backend/src/workspace-documents/workspace-documents.service.ts
index eed5f9a2..444b3333 100644
--- a/backend/src/workspace-documents/workspace-documents.service.ts
+++ b/backend/src/workspace-documents/workspace-documents.service.ts
@@ -26,7 +26,9 @@ export class WorkspaceDocumentsService {
 				},
 			});
 		} catch (e) {
-			throw new NotFoundException();
+			throw new NotFoundException(
+				"The workspace does not exist, or the user lacks the appropriate permissions."
+			);
 		}
 
 		return this.prismaService.document.create({
@@ -52,7 +54,9 @@ export class WorkspaceDocumentsService {
 				},
 			});
 		} catch (e) {
-			throw new NotFoundException();
+			throw new NotFoundException(
+				"The workspace does not exist, or the user lacks the appropriate permissions."
+			);
 		}
 
 		const additionalOptions: Prisma.DocumentFindManyArgs = {};
@@ -111,14 +115,16 @@ export class WorkspaceDocumentsService {
 					workspaceId,
 				},
 			});
-
-			return this.prismaService.document.findUniqueOrThrow({
+			const document = await this.prismaService.document.findUniqueOrThrow({
 				where: {
 					id: documentId,
 				},
 			});
+			return document;
 		} catch (e) {
-			throw new NotFoundException();
+			throw new NotFoundException(
+				"The workspace or document does not exist, or the user lacks the appropriate permissions."
+			);
 		}
 	}
 
@@ -146,7 +152,9 @@ export class WorkspaceDocumentsService {
 				},
 			});
 		} catch (e) {
-			throw new NotFoundException();
+			throw new NotFoundException(
+				"The workspace or document does not exist, or the user lacks the appropriate permissions."
+			);
 		}
 
 		const token = generateRandomKey();
diff --git a/backend/src/workspace-users/workspace-users.service.ts b/backend/src/workspace-users/workspace-users.service.ts
index 5723aba1..dd2ff0bc 100644
--- a/backend/src/workspace-users/workspace-users.service.ts
+++ b/backend/src/workspace-users/workspace-users.service.ts
@@ -21,7 +21,9 @@ export class WorkspaceUsersService {
 				},
 			});
 		} catch (e) {
-			throw new NotFoundException();
+			throw new NotFoundException(
+				"The workspace does not exist, or the user lacks the appropriate permissions."
+			);
 		}
 
 		const additionalOptions: Prisma.UserFindManyArgs = {};
diff --git a/backend/src/workspaces/workspaces.service.ts b/backend/src/workspaces/workspaces.service.ts
index 978f66d0..8c3f39cf 100644
--- a/backend/src/workspaces/workspaces.service.ts
+++ b/backend/src/workspaces/workspaces.service.ts
@@ -25,7 +25,7 @@ export class WorkspacesService {
 		const { conflict } = await this.checkService.checkNameConflict(title);
 
 		if (conflict) {
-			throw new ConflictException();
+			throw new ConflictException("Workspace title is already in use.");
 		}
 
 		const workspace = await this.prismaService.workspace.create({
@@ -63,7 +63,9 @@ export class WorkspacesService {
 
 			return foundWorkspace;
 		} catch (e) {
-			throw new NotFoundException();
+			throw new NotFoundException(
+				"Workspace not found, or the user lacks the appropriate permissions."
+			);
 		}
 	}
 
@@ -114,7 +116,9 @@ export class WorkspacesService {
 				},
 			});
 		} catch (e) {
-			throw new NotFoundException();
+			throw new NotFoundException(
+				"Worksapce does not exist, or the user lacks the appropriate permissions."
+			);
 		}
 
 		const token = generateRandomKey();
diff --git a/frontend/src/hooks/useErrorHandler.ts b/frontend/src/hooks/useErrorHandler.ts
index eb6b553f..768820d7 100644
--- a/frontend/src/hooks/useErrorHandler.ts
+++ b/frontend/src/hooks/useErrorHandler.ts
@@ -1,11 +1,24 @@
 import { useSnackbar } from "notistack";
 import { useCallback } from "react";
 
+interface CustomError extends Error {
+	response?: {
+		data: {
+			error: string;
+			message?: string;
+			statusCode: number;
+		};
+	};
+}
+
 export function useErrorHandler() {
 	const { enqueueSnackbar } = useSnackbar();
 	const handleError = useCallback(
-		(error: Error) => {
-			enqueueSnackbar(error.message || "Something went wrong...", { variant: "error" });
+		(error: CustomError) => {
+			enqueueSnackbar(
+				error.response?.data.message || error.message || "Something went wrong...",
+				{ variant: "error" }
+			);
 		},
 		[enqueueSnackbar]
 	);