Convex Function Creator

Generate secure, type-safe Convex functions following all best practices.

When to Use

• Creating new query functions (read data)
• Creating new mutation functions (write data)
• Creating new action functions (external APIs, long-running)
• Adding API endpoints to your Convex backend

Function Types

Queries (Read-Only)

• Can only read from database
• Cannot modify data or call external APIs
• Cached and reactive
• Run in transactions

import { query } from "./_generated/server";
import { v } from "convex/values";

export const getTask = query({
  args: { taskId: v.id("tasks") },
  returns: v.union(v.object({
    _id: v.id("tasks"),
    text: v.string(),
    completed: v.boolean(),
  }), v.null()),
  handler: async (ctx, args) => {
    return await ctx.db.get(args.taskId);
  },
});

Mutations (Transactional Writes)

• Can read and write to database
• Cannot call external APIs
• Run in ACID transactions
• Automatic retries on conflicts

import { mutation } from "./_generated/server";
import { v } from "convex/values";

export const createTask = mutation({
  args: {
    text: v.string(),
    priority: v.optional(v.union(
      v.literal("low"),
      v.literal("medium"),
      v.literal("high")
    )),
  },
  returns: v.id("tasks"),
  handler: async (ctx, args) => {
    const identity = await ctx.auth.getUserIdentity();
    if (!identity) throw new Error("Not authenticated");

    return await ctx.db.insert("tasks", {
      text: args.text,
      priority: args.priority ?? "medium",
      completed: false,
      createdAt: Date.now(),
    });
  },
});

Actions (External + Non-Transactional)

• Can call external APIs (fetch, AI, etc.)
• Can call mutations via ctx.runMutation
• Cannot directly access database
• No automatic retries
• Use "use node" directive when needing Node.js APIs

Important: If your action needs Node.js-specific APIs (crypto, third-party SDKs, etc.), add "use node" at the top of the file. Files with "use node" can ONLY contain actions, not queries or mutations.

"use node"; // Required for Node.js APIs like OpenAI SDK

import { action } from "./_generated/server";
import { api } from "./_generated/api";
import { v } from "convex/values";
import OpenAI from "openai";

const openai = new OpenAI({ apiKey: process.env.OPENAI_API_KEY });

export const generateTaskSuggestion = action({
  args: { prompt: v.string() },
  returns: v.string(),
  handler: async (ctx, args) => {
    const identity = await ctx.auth.getUserIdentity();
    if (!identity) throw new Error("Not authenticated");

    // Call OpenAI (requires "use node")
    const completion = await openai.chat.completions.create({
      model: "gpt-4",
      messages: [{ role: "user", content: args.prompt }],
    });

    const suggestion = completion.choices[0].message.content;

    // Write to database via mutation
    await ctx.runMutation(api.tasks.createTask, {
      text: suggestion,
    });

    return suggestion;
  },
});

Note: If you only need basic fetch (no Node.js APIs), you can omit "use node". But for third-party SDKs, crypto, or other Node.js features, you must use it.

Required Components

1. Argument Validation

Always define args with validators:

args: {
  id: v.id("tasks"),
  text: v.string(),
  count: v.number(),
  enabled: v.boolean(),
  tags: v.array(v.string()),
  metadata: v.optional(v.object({
    key: v.string(),
  })),
}

2. Return Type Validation

Always define returns:

returns: v.object({
  _id: v.id("tasks"),
  text: v.string(),
})

// Or for arrays
returns: v.array(v.object({ /* ... */ }))

how to use function-creator
CursorClaude CodeClineCodexWindsurfGooseGitHub CopilotVS CodeGemini CLIKiloOpencodeKimi CLIRoo ClineAiderContinueZedBolt.newLovablev0Replit AgentSweepSmol DeveloperDevinCavemanAmpAntigravity
How to use function-creator on Cursor
AI-first code editor with Composer
1
Prerequisites
Before installing skills in Cursor, ensure your development environment meets these requirements:
›Cursor installed and configured on your development machine
›Node.js version 16.0+ with npm package manager (verify with node --version)
›Active project directory or workspace where you want to add function-creator
2
Execute installation command
Execute the skills CLI command in your project's root directory to begin installation:
$npx skills add https://github.com/get-convex/agent-skills --skill function-creatorcopy
The skills CLI fetches function-creator from GitHub repository get-convex/agent-skills and configures it for Cursor.
3
Select Cursor when prompted
The CLI will show a list of available agents. Use arrow keys to navigate and space to select Cursor:
◆ Which agents do you want to install to?
│
│ ── Universal (.agents/skills) ── always included ────
│   • Amp
│   • Antigravity
│   • Cline
│   • Codex
│ ●Cursor(selected)
│   • Cursor
│   • Windsurf
4
Verify installation
Confirm successful installation by checking the skill directory location:
.cursor/skills/function-creator
Reload or restart Cursor to activate function-creator. Access the skill through slash commands (e.g., /function-creator) or your agent's skill management interface.
⚠
Security & Verification Notice
We perform automated surface-level scans (Gen AI Scanner, Socket, Snyk) during installation. These checks detect common vulnerabilities but do not guarantee complete security. Always review skill source code and verify the publisher's reputation before production use.
Skills execute code in your development environment. Always verify the publisher's identity, review recent commits, and test in isolated environments before production deployment.
Additional Resources
›View source code on GitHub›Skills CLI documentation›Learn more about Cursor›What are agent skills?