diff --git a/packages/hydrooj/package.json b/packages/hydrooj/package.json
index 5139ac81a..29464258c 100644
--- a/packages/hydrooj/package.json
+++ b/packages/hydrooj/package.json
@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "2.33.4",
+    "version": "2.33.5",
     "bin": "bin/hydrooj.js",
     "main": "src/loader",
     "module": "src/loader",
@@ -20,6 +20,7 @@
         "detect-browser": "^5.2.0",
         "fs-extra": "^10.0.0",
         "graphql": "^15.5.1",
+        "graphql-scalars": "^1.10.0",
         "js-yaml": "^4.1.0",
         "koa": "^2.13.1",
         "koa-body": "^4.2.0",
diff --git a/packages/hydrooj/src/handler/api.ts b/packages/hydrooj/src/handler/api.ts
index 8a211ef6e..036258348 100644
--- a/packages/hydrooj/src/handler/api.ts
+++ b/packages/hydrooj/src/handler/api.ts
@@ -1,34 +1,78 @@
 import graphql from 'graphql';
-import UserModel from '../model/user';
+import { typeDefs, resolvers } from 'graphql-scalars';
 import { Handler, Route } from '../service/server';
+import * as bus from '../service/bus';
 
-const schemaStr = `\
-type Query {
-    user(id: Int, uname: String, mail: String): User
-    problem(id: Int): String
+const types: Record<string, Record<string, string>> = {};
+const descriptions: Record<string, Record<string, string>> = {};
+const handlers: Record<string, Record<string, any>> = {};
+let root: Record<string, any> = {};
+
+export function registerValue(typeName: string, key: string, value: string, description?: string): void;
+export function registerValue(typeName: string, vals: [string, string, string?][]): void;
+export function registerValue(typeName: string, arg1: [string, string, string?][] | string, value?: string, description?: string) {
+    if (typeof arg1 === 'string') arg1 = [[arg1, value!, description]];
+    for (const [k, v, d] of arg1) {
+        if (!types[typeName]) types[typeName] = { [k]: v };
+        else types[typeName][k] = v;
+        if (d) {
+            if (!descriptions[typeName]) descriptions[typeName] = { [k]: d };
+            else descriptions[typeName][k] = d;
+        }
+    }
+    bus.emit('api/update');
 }
 
-type User {
-    _id: Int!
-    uname: String!
-    mail: String!
-}`;
+export function registerResolver(typeName: string, key: string, value: string, func: Function, description?: string) {
+    registerValue(typeName, key, value, description);
+    if (handlers[typeName]) handlers[typeName][key.split('(')[0].trim()] = func;
+    else handlers[typeName] = { [key.split('(')[0].trim()]: func };
+    bus.emit('api/update');
+}
 
-const schema = graphql.buildSchema(schemaStr);
-const root = {
-    user: (arg, ctx) => {
-        if (arg.id) return UserModel.getById(ctx.domainId, arg.id);
-        if (arg.mail) return UserModel.getByEmail(ctx.domainId, arg.mail);
-        if (arg.uname) return UserModel.getByUname(ctx.domainId, arg.uname);
-        return ctx.user;
-    },
-    problem: async () => { },
-};
+function setDescription(desc: string) {
+    if (desc.includes('\n')) return ['"""', desc, '"""'].join('\n');
+    return JSON.stringify(desc);
+}
+
+function buildSchemaStr() {
+    let res = `${typeDefs.join('\n')}\n`;
+    for (const key in types) {
+        if (descriptions[key]._description) res += `${setDescription(descriptions[key]._description)}\n`;
+        res += `type ${key}{\n`;
+        for (const k in types[key]) {
+            if (descriptions[key][k]) res += `  ${setDescription(descriptions[key][k])}\n`;
+            res += `  ${k}: ${types[key][k]}\n`;
+        }
+        res += '}\n';
+    }
+    return res;
+}
+
+let schemaStr = buildSchemaStr();
+let schema = graphql.buildSchema(schemaStr);
+root = { ...handlers.Query, ...resolvers };
+
+export function rebuild() {
+    try {
+        const str = buildSchemaStr();
+        schema = graphql.buildSchema(str);
+        schemaStr = str;
+        root = { ...handlers.Query, ...resolvers };
+    } catch (e) {
+        console.error(e);
+    }
+}
+bus.on('app/started', () => {
+    rebuild();
+    bus.on('api/update', rebuild);
+});
 
 class ApiHandler extends Handler {
     async get() {
         const q = decodeURIComponent(this.ctx.request.querystring);
         if (q === 'schema') {
+            this.response.type = 'application/json';
             this.response.body = { schema: schemaStr };
         } else if (q) {
             this.response.type = 'application/json';
@@ -38,6 +82,7 @@ class ApiHandler extends Handler {
 
     async post() {
         this.response.type = 'application/json';
+        // FIXME validation for fields like ObjectID doesn't work.
         this.response.body = await graphql.graphql(schema, this.args.query, root, this, this.args.variables);
     }
 }
diff --git a/packages/hydrooj/src/handler/user.ts b/packages/hydrooj/src/handler/user.ts
index 22d598de0..a8dc92a4c 100644
--- a/packages/hydrooj/src/handler/user.ts
+++ b/packages/hydrooj/src/handler/user.ts
@@ -1,4 +1,5 @@
 import moment from 'moment-timezone';
+import { registerResolver, registerValue } from './api';
 import {
     UserAlreadyExistError, InvalidTokenError, VerifyPasswordError,
     UserNotFoundError, SystemError, BlacklistedError,
@@ -22,6 +23,34 @@ import { sendMail } from '../lib/mail';
 import paginate from '../lib/paginate';
 import avatar from '../lib/avatar';
 
+registerValue('User', [
+    ['_id', 'Int!'],
+    ['uname', 'String!'],
+    ['mail', 'String!'],
+    ['perm', 'Int'],
+    ['scope', 'Int'],
+    ['role', 'String'],
+    ['loginat', 'Date'],
+    ['regat', 'Date'],
+    ['priv', 'Int', 'User Privilege'],
+]);
+
+registerResolver('Query', 'user(id: Int, uname: String, mail: String)', 'User', (arg, ctx) => {
+    if (arg.id) return user.getById(ctx.domainId, arg.id);
+    if (arg.mail) return user.getByEmail(ctx.domainId, arg.mail);
+    if (arg.uname) return user.getByUname(ctx.domainId, arg.uname);
+    return ctx.user;
+}, `Get a user by id, uname, or mail.
+Returns current user if no argument is provided.`);
+
+registerResolver('Query', 'users(ids: [Int], search: String)', '[User]', async (arg, ctx) => {
+    if (arg.ids) {
+        const res = await user.getList(ctx.domainId, arg.ids);
+        return Object.keys(res).map((id) => res[+id]);
+    }
+    return arg.search ? await user.getPrefixList(ctx.domainId, arg.search) : [];
+}, 'Get a list of user by ids, or search users with the prefix.');
+
 class UserLoginHandler extends Handler {
     noCheckPermView = true;