> ## Documentation Index
> Fetch the complete documentation index at: https://forst-lang.org/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Generate client types
> Emit .d.ts from Forst with forst generate so Node clients match server shapes.
**`forst generate`** emits TypeScript declarations from the same definitions the compiler validates, so Node clients import shapes that match the server.
To call these functions at runtime, see [Call Forst from Node](/docs/interop/node/call-forst). To call legacy JavaScript from compiled Forst, see [Call JavaScript from Forst](/docs/interop/node/call-javascript).
## Manual types in TypeScript
Without generated types, every API change means updating TS by hand:
```typescript theme={"languages":{"custom":["/languages/forst.json"]}}
interface PlaceOrderInput {
stockKeepingUnit: string; // any string
quantity: number; // any number
}
```
TypeScript cannot express `quantity` must be 1 to 99 unless you add Zod, Effect.Schema, or similar. That is another schema to maintain.
## Types from .ft
Define the shape once in Forst:
```ft theme={"languages":{"custom":["/languages/forst.json"]}}
type PlaceOrderInput = {
stockKeepingUnit: String.Min(1).Max(64),
quantity: Int.Min(1).Max(99),
}
func placeOrder(in: PlaceOrderInput) {
// in is already validated; business logic starts here
}
```
```go theme={"languages":{"custom":["/languages/forst.json"]}}
// forst build
type PlaceOrderInput struct {
stockKeepingUnit string
quantity int
}
func placeOrder(in PlaceOrderInput) {
if len(in.stockKeepingUnit) < 1 || len(in.stockKeepingUnit) > 64 { ... }
if in.quantity < 1 || in.quantity > 99 { ... }
// business logic starts here
}
```
```typescript theme={"languages":{"custom":["/languages/forst.json"]}}
// forst generate → generated/types.d.ts
export interface PlaceOrderInput {
quantity: number;
stockKeepingUnit: string;
}
```
Run:
```bash theme={"languages":{"custom":["/languages/forst.json"]}}
npx forst generate ./path/to/project
```
Output layout (typical):
```text theme={"languages":{"custom":["/languages/forst.json"]}}
generated/
├── types.d.ts # merged type declarations
└── ...
client/ # optional client stubs (see Call Forst from Node)
```
Import in your frontend or BFF:
```typescript theme={"languages":{"custom":["/languages/forst.json"]}}
import type { PlaceOrderInput } from "./generated/types";
async function submitOrder(input: PlaceOrderInput) {
// structural match with server-side Forst types
}
```
## Discovery with `ftconfig.json`
`forst generate` and `forst dev` share **include/exclude** rules from `ftconfig.json`:
```json theme={"languages":{"custom":["/languages/forst.json"]}}
{
"files": {
"include": ["**/*.ft"],
"exclude": [
"**/node_modules/**",
"**/.git/**",
"**/client/**"
]
}
}
```
Pass **`-config`** explicitly or let the CLI search upward from your target directory.
## End-to-end example
The **tictactoe** example in the repository demonstrates merged-package generate:
```bash theme={"languages":{"custom":["/languages/forst.json"]}}
task example:tictactoe:generate
```
See [`examples/in/tictactoe/`](https://github.com/forst-lang/forst/tree/main/examples/in/tictactoe) and [`examples/client-integration/`](https://github.com/forst-lang/forst/tree/main/examples/client-integration).
## Caveats
### Structure only in TypeScript
Generated **`.d.ts`** files reflect field names and types. They do **not** carry runtime rules like **`String.Min(1)`** or **`Int.Max(99)`**. Add client validation yourself, or call the Forst server which validates at the boundary.
### Provider gated exports
Functions that need wired **`Providers(f)`** are excluded from TypeScript emit. The invoke wire stays payload only. See [Providers § Caveats](/docs/language/providers#caveats).
### Nominal error tags
TypeScript **`_tag`** export for nominal errors is still maturing. Treat error payloads as evolving. See [Errors and Result § Caveats](/docs/language/errors-and-result#caveats).
## Related
Invoke generated functions — dev server or built-in HTTP server.
Call legacy `.ts`/`.js` from compiled Forst (`import node`).
Pick your migration path.
Install `@forst/cli` in your project.