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Agent skill

Function Creator

by waynesutton in waynesutton/markdown-site

Create Convex queries, mutations, and actions with proper validation, authentication, and error handling.

MITAuto-check passedBackend & APIs

Install Function Creator

skills CLI
$ npx skills add waynesutton/markdown-site --skill function-creator -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install waynesutton/markdown-site function-creator --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/waynesutton/markdown-site.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/function-creator .claude/skills/function-creator && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
function-creator
GitHub stars
628
Token cost
~1.2k tokens
SKILL.md length
226 words
Files
1
Skills in repo
17
Repo updated
First seen
Licence
MIT

At a glance

Create Convex queries, mutations, and actions with proper validation, authentication, and error handling.

  • Works in 4 steps: Argument Validation → Return Type Validation → Authentication Check → …
  • Implementing new API endpoints
  • SKILL.md covers When to Use, Function Types, Required Components and Internal Functions, plus 1 more section
  • Needs OPENAI_API_KEY

What it does

Function Creator is an agent skill from waynesutton/markdown-site. Create Convex queries, mutations, and actions with proper validation, authentication, and error handling. Use when implementing new API endpoints.

Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Backend & APIs, covering REST APIs and Authentication. It works with Node.js. The repository describes itself as: An open-source publishing framework built for AI agents and developers to ship websites, docs, or blogs. Write markdown, sync from the terminal. Your content is instantly… The licence is MIT.

When your agent uses it

  • Implementing new API endpoints
  • Tasks that involve REST APIs
  • Tasks that involve Authentication

Example prompts

  • “/function-creator”

Requirements

  • Node.js
  • A credential in OPENAI_API_KEY

Workflow steps

4 steps, taken from the step headings in SKILL.md.

  1. Argument Validation
  2. Return Type Validation
  3. Authentication Check
  4. Authorization Check

What it can do on your machine

Read from SKILL.md and the folder at commit 3872c59. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are typescript).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • github.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names these keys or tokens, usually read from environment variables:

    • OPENAI_API_KEY

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Function Creator loads about 1.2k tokens when it runs. Until then it costs about 41 tokens; SKILL.md has 226 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~41
When it runs · the whole SKILL.md, loaded when a task matches
~1.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from waynesutton/markdown-site at commit 3872c59, republished under its MIT licence (© waynesutton). 226 words, ~1,170 tokens.

Download SKILL.mdSave it as .claude/skills/function-creator/SKILL.md (or your agent's skills folder).
name
function-creator
description
Create Convex queries, mutations, and actions with proper validation, authentication, and error handling. Use when implementing new API endpoints.

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
typescript
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
typescript
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
typescript
"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;
  },
});

Note: Keep queries and mutations in files without "use node". Actions that need Node.js go in separate files with "use node".

Required Components

1. Argument Validation

Always define args with validators.

2. Return Type Validation

Always define returns.

3. Authentication Check

Always verify auth in public functions:

typescript
const identity = await ctx.auth.getUserIdentity();
if (!identity) throw new Error("Not authenticated");
4. Authorization Check

Always verify ownership/permissions:

typescript
const task = await ctx.db.get(args.taskId);
if (!task) throw new Error("Task not found");
if (task.userId !== user._id) throw new Error("Unauthorized");

Internal Functions

For backend-only functions (called by scheduler, other functions):

typescript
import { internalMutation } from "./_generated/server";

export const processExpiredTasks = internalMutation({
  args: {},
  handler: async (ctx) => {
    const now = Date.now();
    const expired = await ctx.db
      .query("tasks")
      .withIndex("by_due_date", q => q.lt("dueDate", now))
      .collect();

    for (const task of expired) {
      await ctx.db.patch(task._id, { status: "expired" });
    }
  },
});

Checklist

  • args defined with validators
  • returns defined with validator
  • Authentication check (ctx.auth.getUserIdentity())
  • Authorization check (ownership/permissions)
  • All promises awaited
  • Indexed queries (no .filter() on queries)
  • Error handling with descriptive messages
  • Scheduled functions use internal.* not api.*
  • If using Node.js APIs: "use node" at top of file
  • If file has "use node": Only actions (no queries/mutations)

Source: https://github.com/get-convex/convex-agent-plugins

© waynesutton, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .claude/function-creator of waynesutton/markdown-site.

Open the folder on GitHubat commit 3872c59

Compare with similar skills

Function Creator next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Function Creator compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Function Creator this skillwaynesutton/markdown-site628—~1.2kAutomated safety check: PassMIT
Nodejs Express Serverever-works/ever-works158—~965Automated safety check: PassAGPL-3.0
Senior Backendalirezarezvani/claude-skills28k1 repos~3.8kAutomated safety check: PassMIT
Adynato Web APImajiayu000/claude-skill-registry6661 repos~2kAutomated safety check: PassMIT
Nodejs Backend Patternsever-works/ever-works15817 repos~4kAutomated safety check: PassAGPL-3.0
Databuddydatabuddy-analytics/Databuddy1.2k—~2.1kAutomated safety check: PassAGPL-3.0

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Works with

Categories

Questions about Function Creator

What does Function Creator do?

Create Convex queries, mutations, and actions with proper validation, authentication, and error handling. Function Creator is an agent skill from waynesutton/markdown-site. Create Convex queries, mutations, and actions with proper validation, authentication, and error handling.

When should I use Function Creator?

Function Creator fits situations like: implementing new API endpoints; tasks that involve REST APIs; tasks that involve Authentication.

How do I install Function Creator in Claude Code?

Run `npx skills add waynesutton/markdown-site --skill function-creator -a claude-code`. Or copy the skill folder (.claude/function-creator in waynesutton/markdown-site) into .claude/skills/function-creator in your project. Claude Code loads it when a task matches its description.

How do I install Function Creator in Codex?

Run `npx skills add waynesutton/markdown-site --skill function-creator -a codex`. Or copy the skill folder (.claude/function-creator in waynesutton/markdown-site) into .agents/skills/function-creator in your project. Codex loads it when a task matches its description.

Can I use Function Creator in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add waynesutton/markdown-site --skill function-creator -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/function-creator, .gemini/skills/function-creator, .github/skills/function-creator and .opencode/skills/function-creator in your project.

What does Function Creator need to run?

Going by SKILL.md and its folder, Function Creator needs credentials named OPENAI_API_KEY. Our summary lists: Node.js; A credential in OPENAI_API_KEY.

Does Function Creator access the network?

SKILL.md names 1 domain. As links in the text: github.com. This is read from the text; nothing was executed.

Is Function Creator safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Function Creator use?

Function Creator is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Function Creator use?

About 1.2k tokens (SKILL.md is roughly 4.7k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Function Creator?

Skills that share tags, products or a category with Function Creator: Nodejs Express Server (ever-works/ever-works, 158 stars), Senior Backend (alirezarezvani/claude-skills, 28k stars), Adynato Web API (majiayu000/claude-skill-registry, 666 stars) and Nodejs Backend Patterns (ever-works/ever-works, 158 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Function Creator?

waynesutton (a GitHub user) maintains it in waynesutton/markdown-site, which has 628 GitHub stars. The repository holds 17 skills in this directory. The repository was last updated on May 20, 2026.

Source: waynesutton/markdown-site on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.