# tRPC

URL: https://tailrace.dev/docs/integrations/trpc

> Procedure middleware for tRPC - check input and output at the tool boundary, throw TRPCError on block.



Enforce data policy on tRPC procedure input and result data. This is the **tool** boundary, not an OpenAI REST gateway.

## Quickstart [#quickstart]

```ts
import { createTailrace } from "@tailrace/core";
import { createTailraceMiddleware, withTrpc } from "@tailrace/trpc";
import { initTRPC } from "@trpc/server";

const t = initTRPC.create();

const governed = createTailraceMiddleware(createTailrace(), {
  agent: "api",
  name: ({ path }) => path,
});
export const procedure = t.procedure.use(governed);

// Fluent alternative
const tr = withTrpc(createTailrace());
export const procedure2 = t.procedure.use(tr.middleware({ agent: "api" }));
```

Peer: `@trpc/server` `>=10`. Non-streaming queries and mutations only in v0.1.

## Boundaries covered [#boundaries-covered]

| Surface | Tailrace boundary                          | Direction |
| ------- | ------------------------------------------ | --------- |
| Input   | `{ kind: "tool", name, direction: "out" }` | Outbound  |
| Output  | `{ kind: "tool", name, direction: "in" }`  | Inbound   |

Block → `TRPCError` (`BAD_REQUEST`) with a value-free message. Tokenize / mask rewrite input or result data in place.

## Guides [#guides]

* [Govern tRPC procedures](/docs/guides/govern-trpc-procedures)
* [Boundaries](/docs/concepts/boundaries)

## Reference [#reference]

* [tRPC package](/docs/reference/trpc)