markdown-site: Skill for Claude Code

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

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
• Use "use node" directive when needing Node.js APIs

"use node";

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");

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

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

    await ctx.runMutation(api.tasks.createTask, { text: suggestion });
    return suggestion;
  },
});