# GRAPHQL API

> Design and implement GraphQL APIs with proper schema design, resolvers, and best practices.

- Skill: `heldinhow/graphql-api` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add heldinhow/graphql-api`
- Raw SKILL.md: https://api.skillmd.com/api/skills/heldinhow/graphql-api/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: Heldinhow (https://skillmd.com/u/heldinhow)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/heldinhow/graphql-api

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# GraphQL API

## Overview
GraphQL provides a flexible query language for APIs with precise data requirements. This skill should be invoked when building flexible APIs needing nested data fetching, multiple data source aggregation, or client-controlled queries.

## Core Principles
- **Schema-Driven**: Define types, queries, mutations in schema
- **Resolver Implementation**: Map schema fields to data sources
- **DataLoader**: Prevent N+1 queries with batching
- **Validation**: Validate inputs and handle errors properly

## Preparation Checklist
- [ ] Choose GraphQL server (Apollo, GraphQL Yoga, Mercury)
- [ ] Design schema with types, queries, mutations
- [ ] Plan resolver structure
- [ ] Set up DataLoader for optimization

## Step-by-Step Process
1. **Define Schema**: Write SDL with types, queries, mutations
2. **Implement Resolvers**: Create resolver functions
3. **Optimize**: Add DataLoader for batching
4. **Validate**: Add input validation
5. **Document**: Set up Playground/GraphiQL
6. **Monitor**: Add query complexity analysis

## Do's and Don'ts
- ✅ **Do** use DataLoader to prevent N+1 queries
- ✅ **Do** validate all inputs
- ✅ **Do** set query complexity limits
- ❌ **Don't** expose internal database IDs
- ❌ **Don't** skip error handling
- ❌ **Don't** allow unbounded queries

## Anti-Patterns
- **N+1 Queries**: Not using DataLoader
- **No Limits**: Allowing unbounded queries
- **Internal Exposure**: Leaking implementation details
- **Error Leaks**: Exposing stack traces