Procedure metadata allows you to add an optional procedure specific meta property which will be available in all middleware function parameters.

tip

Use metadata together with trpc-openapi if you want to expose REST-compatible endpoints for your application.

tsx

import { initTRPC } from '@trpc/server';

// [...]

interface Meta {

authRequired: boolean;

}

export const t = initTRPC.context<Context>().meta<Meta>().create();

export const appRouter = t.router({

// [...]

});

Example with per route authentication settings​

server.ts

tsx

import { initTRPC } from '@trpc/server';

// [...]

interface Meta {

authRequired: boolean;

}

export const t = initTRPC.context<Context>().meta<Meta>().create();

export const authedProcedure = t.procedure.use(async (opts) => {

const { meta, next, ctx } = opts;

// only check authorization if enabled

if (meta?.authRequired && !ctx.user) {

`throw new TRPCError({ code: 'UNAUTHORIZED' });`

}

return next();

});

export const appRouter = t.router({

hello: authedProcedure.meta({ authRequired: false }).query(() => {

`return {`

  `greeting: 'hello world',`

`};`

}),

protectedHello: authedProcedure.meta({ authRequired: true }).query(() => {

`return {`

  `greeting: 'hello-world',`

`};`

}),

});

You can set default values for your meta type, and if you chain meta on top of a base procedure it will be shallow merged.

tsx

import { initTRPC } from '@trpc/server';

interface Meta {

authRequired: boolean;

role?: 'user' | 'admin'

}

export const t = initTRPC

.context<Context>()

.meta<Meta>()

.create({

`// Set a default value`

`defaultMeta: { authRequired: false }`

});

const publicProcedure = t.procedure

// ^ Default Meta: { authRequired: false }

const authProcedure = publicProcedure

.use(authMiddleware)

.meta({

`authRequired: true;`

`role: 'user'`

});

// ^ Meta: { authRequired: true, role: 'user' }

const adminProcedure = authProcedure

.meta({

`role: 'admin'`

});

// ^ Meta: { authRequired: true, role: 'admin' }