tRPC OpenAPI

Name: tRPC OpenAPI
Author: trpc

Generate an OpenAPI 3.1 spec from a tRPC router with @trpc/openapi (CLI or programmatic) and a typed REST client with @hey-api/openapi-ts.

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Context cost: 2.2k tokensestimated from the bundle, loaded when it triggers
Bundle: 1 file · 8.9 kBtext throughout, nothing executable
Licence: MITpaid listing
Last change: —no release on file
Servers it uses: Noneruns standalone

What it does

Generate OpenAPI 3.1 spec from a tRPC router with @trpc/openapi CLI or programmatic API. Generate typed REST client with @hey-api/openapi-ts and configureTRPCHeyApiClient(). Configure transformers (superjson, EJSON) for generated clients. Alpha status.

Installed, it changes the agent in these ways.

What this skill changes about the agent is not written down here yet. The listing was collected from its source, and the description is in its own SKILL.md.

Workflow

Runs a procedure end to end.

openapitrpcrestcodegen

Filed under

API Development

The skill itself

This is the whole product. A skill is instructions the model reads, so there is nothing behind the listing you cannot see first — the front matter loads with every session, and the body below it loads when the skill triggers.

SKILL.md8.9 kB · 301 lines

--- name: openapi description: > Generate OpenAPI 3.1 spec from a tRPC router with @trpc/openapi CLI or programmatic API. Generate typed REST client with @hey-api/openapi-ts and configureTRPCHeyApiClient(). Configure transformers (superjson, EJSON) for generated clients. Alpha status. type: composition library: trpc library_version: '11.16.0-alpha' requires: - server-setup sources: - 'trpc/trpc:www/docs/client/openapi.md' - 'trpc/trpc:packages/openapi/test/heyapi.test.ts' - 'trpc/trpc:examples/openapi-codegen/' ---

19# tRPC -- OpenAPI

21> **Alpha**: @trpc/openapi is versioned as 11.x.x-alpha. APIs may change without notice.

23## Setup

25### 1. Install

27```bash

28pnpm add @trpc/openapi

29```

31For HeyAPI client generation:

33```bash

34pnpm add @hey-api/openapi-ts -D

35```

37### 2. Generate the OpenAPI spec

39The generator statically analyses your router's TypeScript types. It never executes your code.

41**CLI:**

43```bash

44pnpm exec trpc-openapi ./src/server/index.ts -e appRouter -o openapi.json --title "My API" --version 1.0.0

45```

47| Option | Default | Description |

48| --------------------- | -------------- | --------------------------- |

49| -e, --export <name> | AppRouter | Name of the exported router |

50| -o, --output <file> | openapi.json | Output file path |

51| --title <text> | tRPC API | OpenAPI info.title |

52| --version <ver> | 0.0.0 | OpenAPI info.version |

54**Programmatic:**

56```ts

57import { generateOpenAPIDocument } from '@trpc/openapi';

59const doc = await generateOpenAPIDocument('./src/server/index.ts', {

60 exportName: 'appRouter',

61 title: 'My API',

62 version: '1.0.0',

63});

64```

66### 3. Generate a HeyAPI client from the spec

68```ts

69// scripts/codegen.ts

70import { rmSync, writeFileSync } from 'node:fs';

71import * as path from 'node:path';

72import { fileURLToPath } from 'node:url';

73import { createClient } from '@hey-api/openapi-ts';

74import { generateOpenAPIDocument } from '@trpc/openapi';

75import { createTRPCHeyApiTypeResolvers } from '@trpc/openapi/heyapi';

77const __filename = fileURLToPath(import.meta.url);

78const __dirname = path.dirname(__filename);

80const routerPath = path.resolve(__dirname, '..', 'server', 'index.ts');

81const outputDir = path.resolve(__dirname, '..', 'client', 'generated');

82const specPath = path.resolve(__dirname, '..', '..', 'openapi.json');

84async function main() {

85 const doc = await generateOpenAPIDocument(routerPath, {

86 exportName: 'appRouter',

87 title: 'Example API',

88 version: '1.0.0',

89 });

91 writeFileSync(specPath, JSON.stringify(doc, null, 2) + '\n');

93 rmSync(outputDir, { recursive: true, force: true });

95 await createClient({

96 input: specPath,

97 output: outputDir,

98 plugins: [

99 {

100 name: '@hey-api/typescript',

101 '~resolvers': createTRPCHeyApiTypeResolvers(),

102 },

103 {

104 name: '@hey-api/sdk',

105 operations: { strategy: 'single' },

106 },

107 ],

108 });

109}

110

111main().catch((err) => {

112 console.error(err);

113 process.exit(1);

114});

115```

116

117Run it:

118

119```bash

120pnpm tsx scripts/codegen.ts

121```

122

123### 4. Configure and use the generated client at runtime

124

125```ts

126import { configureTRPCHeyApiClient } from '@trpc/openapi/heyapi';

127import { client } from './generated/client.gen';

128import { Sdk } from './generated/sdk.gen';

129

130configureTRPCHeyApiClient(client, {

131 baseUrl: 'http://localhost:3000',

132});

133const sdk = new Sdk({ client });

134

135// Queries -> GET, Mutations -> POST

136const result = await sdk.greeting({ query: { input: { name: 'World' } } });

137const user = await sdk.user.create({ body: { name: 'Bob', age: 30 } });

138```

139

140## Core Patterns

141

142### CLI quick spec generation

143

144```bash

145# Default export name "AppRouter", output "openapi.json"

146pnpm exec trpc-openapi ./src/server/router.ts

147

148# Custom export name and output

149pnpm exec trpc-openapi ./src/server/router.ts -e appRouter -o api.json --title "My API" --version 1.0.0

150```

151

152### HeyAPI codegen with type resolvers (transformer setup)

153

154When the server uses a transformer, pass createTRPCHeyApiTypeResolvers() to the @hey-api/typescript plugin so generated types use Date instead of string for date-time fields and bigint for bigint fields:

155

156```ts

157import { createClient } from '@hey-api/openapi-ts';

158import { createTRPCHeyApiTypeResolvers } from '@trpc/openapi/heyapi';

159

160await createClient({

161 input: './openapi.json',

162 output: './generated',

163 plugins: [

164 {

165 name: '@hey-api/typescript',

166 '~resolvers': createTRPCHeyApiTypeResolvers(),

167 },

168 {

169 name: '@hey-api/sdk',

170 operations: { strategy: 'single' },

171 },

172 ],

173});

174```

175

176### Runtime client with superjson transformer

177

178When the tRPC server uses superjson, the client must be configured with the same transformer:

179

180```ts

181// src/shared/transformer.ts

182import superjson from 'superjson';

183

184export const transformer = superjson;

185```

186

187```ts

188// src/server/trpc.ts

189import { initTRPC } from '@trpc/server';

190import { transformer } from '../shared/transformer';

191

192const t = initTRPC.create({ transformer });

193export const router = t.router;

194export const publicProcedure = t.procedure;

195```

196

197```ts

198// src/client/index.ts

199import { configureTRPCHeyApiClient } from '@trpc/openapi/heyapi';

200import superjson from 'superjson';

201import { client } from './generated/client.gen';

202import { Sdk } from './generated/sdk.gen';

203

204configureTRPCHeyApiClient(client, {

205 baseUrl: 'http://localhost:3000',

206 transformer: superjson,

207});

208const sdk = new Sdk({ client });

209

210const event = await sdk.getEvent({

211 query: { input: { id: 'evt_1', at: new Date('2025-06-15T10:00:00Z') } },

212});

213// event.data.result.data.at is a Date object

214```

215

216### MongoDB EJSON transformer (cross-language)

217

218For non-TypeScript clients, EJSON provides a language-agnostic serialization format:

219

220```ts

221import type { TRPCDataTransformer } from '@trpc/server';

222import type { Document } from 'bson';

223import { EJSON } from 'bson';

224

225export const ejsonTransformer: TRPCDataTransformer = {

226 serialize: (value) => EJSON.serialize(value),

227 deserialize: (value) => EJSON.deserialize(value as Document),

228};

229```

230

231```ts

232import { configureTRPCHeyApiClient } from '@trpc/openapi/heyapi';

233import { client } from './generated/client.gen';

234import { ejsonTransformer } from './transformer';

235

236configureTRPCHeyApiClient(client, {

237 baseUrl: 'http://localhost:3000',

238 transformer: ejsonTransformer,

239});

240```

241

242### Response shape

243

244All tRPC HTTP responses follow the envelope format. Access data through result.data:

245

246```ts

247const listResult = await sdk.user.list();

248const users = listResult.data?.result.data; // the actual return value

249

250const createResult = await sdk.user.create({ body: { name: 'nick' } });

251const user = createResult.data?.result.data;

252// user.createdAt instanceof Date === true (when transformer is configured)

253```

254

255### Descriptions in the spec

256

257Zod .describe() calls and JSDoc comments on types, routers, and procedures become description fields in the generated OpenAPI spec. No annotations or decorators required.

258

259## Common Mistakes

260

261### Missing transformer config in HeyAPI client

262

263When the tRPC server uses superjson or another transformer, the generated HeyAPI client must also be configured with the same transformer via configureTRPCHeyApiClient(client, { transformer }). Without this, Date, Map, Set, and other non-JSON types will be silently wrong at runtime -- they arrive as raw serialized objects instead of their native types.

264

265Wrong:

266

267```ts

268configureTRPCHeyApiClient(client, {

269 baseUrl: 'http://localhost:3000',

270 // missing transformer -- Dates will be broken

271});

272```

273

274Right:

275

276```ts

277configureTRPCHeyApiClient(client, {

278 baseUrl: 'http://localhost:3000',

279 transformer: superjson, // must match server's transformer

280});

281```

282

283### Expecting subscriptions in OpenAPI spec

284

285Subscriptions are currently excluded from OpenAPI spec generation. The generator silently skips any procedure with type: 'subscription'. SSE subscription support is planned but not yet available.

286

287### Forgetting createTRPCHeyApiTypeResolvers when using a transformer

288

289Without the type resolvers plugin, HeyAPI generates string types for date-time fields instead of Date. The createTRPCHeyApiTypeResolvers() function maps date/date-time format to Date and bigint format to bigint in the generated TypeScript SDK.

290

291### Using the wrong export name

292

293The CLI defaults to --export AppRouter (the type). If your file exports the router value as appRouter, pass -e appRouter. If the export is not found, the error message lists all available exports from the file.

294

295## See Also

296

297- **server-setup** -- Required. Define routers and procedures before generating the spec.

298- **superjson** -- Transformer configuration for server and client. OpenAPI clients need matching transformer config.

299- **validators** -- Zod .describe() calls propagate into OpenAPI description fields.

300- Full working example: examples/openapi-codegen/

301

In the file

SKILL.md1,092 words

Files1

LicenceMIT

Why you can read it

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What it costs in context

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≈130

always loaded

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2,095

on trigger

The instruction body, read only when the skill fires.

1.1%

of a 200k window

Ten skills this size would take about 11% of the window before you open a file.

050k100k150k200k context window

2.2k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Middling. Fine to keep on in a project where you use it weekly, worth unloading in one where you never do.

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Prose, not code

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What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

If this is not it

15 other skills in API Development

What is in the bundle

1 file, 8.9 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

SKILL.md8.9 kB

What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 1 file you can review in full before installing. The MIT licence covers the templates and examples as well as the instructions.

Install

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$39 once

tRPC OpenAPI · MIT · trpc

one-time

Price$39 once

LicenceMIT — the author’s, unchanged by this purchase

Paid throughStripe, once, on the card you add at the checkout

Keeps workingfor good — the files are yours once they are on disk

Updatesevery update its author ships, delivered through this account

You can read the whole bundle before paying — the SKILL.md above is the product, not a preview of it. What the money buys is the delivery: the folder packaged and handed to your machine by key, every update its author ships, and our support if it does not do what this listing says. The terms of use are MIT, set by the author and unchanged by buying it here.

Payment runs through Stripe, on a page like this one rather than a redirect. Once there is an account it joins the same mcprush invoice as everything else you run, so there is never a second card to enter.

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Referencetrpc/trpc-openapi

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