tRPC Scaffolder Skill | Agent Skills

tRPC Scaffolder

Automate creation of type-safe tRPC endpoints with Zod validation.

TL;DR: Run scripts to create routers/schemas, register in _app.ts, validate with scripts.

Auto-Triggers

Auto-triggered by keywords:

"new endpoint", "create endpoint", "tRPC procedure"
"new router", "API", "Zod schema"

Quick Standards

File Locations

lib/trpc/routers/
  _app.ts          # Register all routers here ⚠️
  {name}.ts        # Router files

lib/trpc/schemas/
  {entity}.schema.ts  # Zod schemas

Router Pattern

export const nameRouter = router({
  doThing: publicProcedure
    .input(inputSchema)
    .output(outputSchema)
    .mutation(async ({ input }) => { /* logic */ }),
});

Schema Pattern

export const inputSchema = z.object({
  field: z.string().min(1),
});

export type Input = z.infer<typeof inputSchema>;  // ⚠️ Required!

Registration (Required!)

// In _app.ts
export const appRouter = router({
  ai: aiRouter,
  name: nameRouter,  // ⬅️ Add new routers here
});

Run Scripts

Create Router

./.claude/skills/trpc-scaffolder/scripts/create-router.sh user
# Creates: lib/trpc/routers/user.ts
# ⚠️ Remember to register in _app.ts!

Add Procedure

./.claude/skills/trpc-scaffolder/scripts/add-procedure.sh ai getHints query
# Outputs code snippet to add to router

Create Schema

./.claude/skills/trpc-scaffolder/scripts/create-schema.sh hint
# Creates: lib/trpc/schemas/hint.schema.ts

Validate Setup

./.claude/skills/trpc-scaffolder/scripts/validate-trpc.sh
# Checks: router registration, type exports

Quick Reference

Query vs Mutation

| Type | Use For | Method | |------|---------|--------| | Query | Fetch data (GET) | .query(async ({ input }) => ...) | | Mutation | Modify data (POST/PUT/DELETE) | .mutation(async ({ input }) => ...) |

Common Zod Patterns

| Type | Pattern | Example | |------|---------|---------| | String | z.string().min(1).max(100) | Name validation | | Number | z.number().int().min(0).max(10) | Difficulty 0-10 | | Email | z.string().email() | Email validation | | Optional | z.string().optional() | Optional field | | Array | z.array(z.string()).min(1) | At least 1 item | | Enum | z.enum(["a", "b", "c"]) | Fixed choices | | Object | z.object({ field: z.string() }) | Nested object |

Naming Conventions

Routers: {domain}Router (e.g., aiRouter, userRouter)
Procedures: camelCase (e.g., generateQuestions, getHints)
Schemas: {action}{Entity}{Input\|Output}Schema
Files: {entity}.schema.ts, {domain}.ts

Error Codes

| Code | When | Example | |------|------|---------| | NOT_FOUND | Resource doesn't exist | User not found | | BAD_REQUEST | Invalid input | Validation failed | | UNAUTHORIZED | Not authenticated | Login required | | FORBIDDEN | Not authorized | Access denied | | INTERNAL_SERVER_ERROR | Server error | API failure |

Common Fixes

Router Not Registered

// ❌ Forgot this step
// ✅ Add to _app.ts:
import { userRouter } from "./user";
export const appRouter = router({ ai: aiRouter, user: userRouter });

Missing Type Exports

// ❌ Schema without types
export const userSchema = z.object({ name: z.string() });

// ✅ Always export inferred types
export type User = z.infer<typeof userSchema>;

Wrong Procedure Type

// ❌ Using mutation for fetching data
getData: publicProcedure.mutation(...)

// ✅ Use query for GET operations
getData: publicProcedure.query(...)

Schema Validation Error

// ❌ No validation
field: z.string()

// ✅ Add constraints
field: z.string().min(1, "Field is required")

When to Load Additional Docs

SKILL.md is self-sufficient for:

Creating routers and schemas
Running scripts
Fixing common errors

Load additional docs when needed:

| Need | Load | |------|------| | Step-by-step tutorial | docs/quick-start-guide.md | | Advanced Zod patterns | docs/trpc-patterns.md (lines 1-80) | | Error handling strategies | docs/trpc-patterns.md (lines 150-220) | | Testing procedures | docs/trpc-patterns.md (lines 220-270) | | Context & middleware | docs/trpc-patterns.md (lines 80-150) |

Code examples:

✅ Perfect: examples/good-router.ts, examples/good-schema.ts

Full project docs: Docs/api-design.md, Docs/api-transition/trpc-migration.md

Version: 1.0.0 | Updated: October 2025 Pattern: Follows quality-reviewer structure (optimized)

Agent Skills: tRPC Scaffolder

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