diff --git a/packages/misskey-js/src/api.types.ts b/packages/misskey-js/src/api.types.ts
index 29e6d10fa5..3432cad4ce 100644
--- a/packages/misskey-js/src/api.types.ts
+++ b/packages/misskey-js/src/api.types.ts
@@ -1,13 +1,15 @@
 import { Endpoints as Gen } from './autogen/endpoint.js';
 import { UserDetailed } from './autogen/models.js';
-import { AdminRolesCreateRequest, AdminRolesCreateResponse, UsersShowRequest, UsersShowErrors } from './autogen/entities.js';
+import { AdminRolesCreateRequest, AdminRolesCreateResponse, UsersShowRequest, UsersShowErrors, AdminRolesCreateErrors } from './autogen/entities.js';
 import {
 	PartialRolePolicyOverride,
 	SigninFlowRequest,
 	SigninFlowResponse,
+	SigninFlowErrors,
 	SigninWithPasskeyInitResponse,
 	SigninWithPasskeyRequest,
 	SigninWithPasskeyResponse,
+	SigninWithPasskeyErrors,
 	SignupPendingRequest,
 	SignupPendingResponse,
 	SignupRequest,
@@ -88,6 +90,7 @@ export type Endpoints = Overwrite<
 		'signin-flow': {
 			req: SigninFlowRequest;
 			res: SigninFlowResponse;
+			errors: SigninFlowErrors;
 		},
 		'signin-with-passkey': {
 			req: SigninWithPasskeyRequest;
@@ -104,10 +107,12 @@ export type Endpoints = Overwrite<
 					$default: SigninWithPasskeyInitResponse;
 				},
 			},
+			errors: SigninWithPasskeyErrors;
 		},
 		'admin/roles/create': {
 			req: Overwrite<AdminRolesCreateRequest, { policies: PartialRolePolicyOverride }>;
 			res: AdminRolesCreateResponse;
+			errors: AdminRolesCreateErrors;
 		}
 	}
 >
diff --git a/packages/misskey-js/src/entities.ts b/packages/misskey-js/src/entities.ts
index 0a483f5741..90ee39f530 100644
--- a/packages/misskey-js/src/entities.ts
+++ b/packages/misskey-js/src/entities.ts
@@ -309,7 +309,15 @@ export type SigninFlowResponse = {
 	authRequest: PublicKeyCredentialRequestOptionsJSON;
 };
 
-export type SigninErrors = {
+type WebAuthnServiceErrors = {
+	id: '2d16e51c-007b-4edd-afd2-f7dd02c947f6', // Invalid context (WebAuthnService)
+} | {
+	id: '36b96a7d-b547-412d-aeed-2d611cdc8cdc', // Unknown WebAuthn Key (WebAuthnService)
+} | {
+	id: 'b18c89a7-5b5e-4cec-bb5b-0419f332d430', // Verification failed (WebAuthnService)
+};
+
+export type SigninFlowErrors = {
 	message: 'Too many failed attempts to sign in. Try again later.',
 	code: 'TOO_MANY_AUTHENTICATION_FAILURES',
 	id: '22d05606-fbcf-421a-a2db-b32610dcfd1b',
@@ -325,7 +333,7 @@ export type SigninErrors = {
 	id: 'cdf1235b-ac71-46d4-a3a6-84ccce48df6f', // Invalid one-time password
 } | {
 	id: '93b86c4b-72f9-40eb-9815-798928603d1e', // Invalid passkey credential
-};
+} | WebAuthnServiceErrors;
 
 export type SigninWithPasskeyRequest = {
 	credential?: AuthenticationResponseJSON;
@@ -341,6 +349,24 @@ export type SigninWithPasskeyResponse = {
 	signinResponse: SigninFlowResponse & { finished: true };
 };
 
+export type SigninWithPasskeyErrors = {
+	message: 'Too many failed attempts to sign in. Try again later.',
+	code: 'TOO_MANY_AUTHENTICATION_FAILURES',
+	id: '22d05606-fbcf-421a-a2db-b32610dcfd1b',
+} | {
+	id: '4e30e80c-e338-45a0-8c8f-44455efa3b76', // Internal server error
+} | {
+	id: '1658cc2e-4495-461f-aee4-d403cdf073c1', // No Context
+} | {
+	id: '932c904e-9460-45b7-9ce6-7ed33be7eb2c', // Invalid credentials
+} | {
+	id: '652f899f-66d4-490e-993e-6606c8ec04c3', // User not found
+} | {
+	id: 'e03a5f46-d309-4865-9b69-56282d94e1eb', // User is suspended
+} | {
+	id: '2d84773e-f7b7-4d0b-8f72-bb69b584c912', // Passwordless Login is disabled
+} | WebAuthnServiceErrors;
+
 type Values<T extends Record<PropertyKey, unknown>> = T[keyof T];
 
 export type PartialRolePolicyOverride = Partial<{[k in keyof RolePolicies]: Omit<Values<Role['policies']>, 'value'> & { value: RolePolicies[k] }}>;