encore-api

Instructions

When creating API endpoints with Encore.ts, follow these patterns:

1. Import the API module

import { api } from "encore.dev/api";

2. Define typed request/response interfaces

Always define explicit TypeScript interfaces for request and response types:

interface CreateUserRequest {
  email: string;
  name: string;
}

interface CreateUserResponse {
  id: string;
  email: string;
  name: string;
}

3. Create the endpoint

export const createUser = api(
  { method: "POST", path: "/users", expose: true },
  async (req: CreateUserRequest): Promise<CreateUserResponse> => {
    // Implementation
  }
);

API Options

| Option | Type | Description | |--------|------|-------------| | method | string | HTTP method: GET, POST, PUT, PATCH, DELETE | | path | string | URL path, supports :param and *wildcard | | expose | boolean | If true, accessible from outside (default: false) | | auth | boolean | If true, requires authentication | | sensitive | boolean | If true, redacts request/response payloads from traces |

Request/Response Patterns

Encore supports four endpoint configurations:

// Both request and response
export const createUser = api(
  { method: "POST", path: "/users", expose: true },
  async (req: CreateRequest): Promise<CreateResponse> => { ... }
);

// Response only (no request body)
export const listUsers = api(
  { method: "GET", path: "/users", expose: true },
  async (): Promise<ListResponse> => { ... }
);

// Request only (no response body)
export const deleteUser = api(
  { method: "DELETE", path: "/users/:id", expose: true },
  async (req: DeleteRequest): Promise<void> => { ... }
);

// Neither request nor response
export const ping = api(
  { method: "GET", path: "/ping", expose: true },
  async (): Promise<void> => { ... }
);

Custom HTTP Status Codes

Include an HttpStatus field in your response to return custom status codes:

import { api, HttpStatus } from "encore.dev/api";

interface CreateResponse {
  id: string;
  status: HttpStatus;
}

export const create = api(
  { method: "POST", path: "/items", expose: true },
  async (req: CreateRequest): Promise<CreateResponse> => {
    const item = await createItem(req);
    return { id: item.id, status: HttpStatus.Created };  // Returns 201
  }
);

Parameter Types

Path Parameters

// Path: "/users/:id"
interface GetUserRequest {
  id: string;  // Automatically mapped from :id
}

Query Parameters

import { Query } from "encore.dev/api";

interface ListUsersRequest {
  limit?: Query<number>;
  offset?: Query<number>;
}

Headers

import { Header } from "encore.dev/api";

interface WebhookRequest {
  signature: Header<"X-Webhook-Signature">;
  payload: string;
}

Cookies

import { Cookie } from "encore.dev/api";

interface SessionRequest {
  session?: Cookie<"session">;
  settings?: Cookie<"user-settings">;
}

Request Validation

Encore validates requests at runtime using TypeScript types. Add constraints for stricter validation:

import { api } from "encore.dev/api";
import { Min, Max, MinLen, MaxLen, IsEmail, IsURL } from "encore.dev/validate";

interface CreateUserRequest {
  email: string & IsEmail;                    // Must be valid email
  username: string & MinLen<3> & MaxLen<20>;  // 3-20 characters
  age: number & Min<13> & Max<120>;           // Between 13 and 120
  website?: string & IsURL;                   // Optional, must be URL if provided
}

Combining Validation Rules

Use & for AND logic (must pass all rules) and | for OR logic (must pass at least one):

import { IsEmail, IsURL, MinLen, MaxLen } from "encore.dev/validate";

interface ContactRequest {
  // Must be valid email OR valid URL
  contact: string & (IsEmail | IsURL);
  // Must be 5-100 chars AND be a valid URL
  website: string & MinLen<5> & MaxLen<100> & IsURL;
}

Available Validators

| Validator | Applies To | Example | |-----------|-----------|---------| | Min<N> | number | age: number & Min<18> | | Max<N> | number | count: number & Max<100> | | MinLen<N> | string, array | name: string & MinLen<1> | | MaxLen<N> | string, array | tags: string[] & MaxLen<10> | | IsEmail | string | email: string & IsEmail | | IsURL | string | link: string & IsURL | | StartsWith<S> | string | id: string & StartsWith<"usr_"> | | EndsWith<S> | string | file: string & EndsWith<".json"> | | MatchesRegexp<R> | string | code: string & MatchesRegexp<"^[A-Z]{3}$"> |

Validation Error Response

Invalid requests return 400 with details:

{
  "code": "invalid_argument",
  "message": "validation failed",
  "details": { "field": "email", "error": "must be a valid email" }
}

Error Handling

Use APIError for proper HTTP error responses:

import { APIError, ErrCode } from "encore.dev/api";

// Throw with error code
throw new APIError(ErrCode.NotFound, "user not found");

// Or use shorthand
throw APIError.notFound("user not found");
throw APIError.invalidArgument("email is required");
throw APIError.unauthenticated("invalid token");

Common Error Codes

| Code | HTTP Status | Usage | |------|-------------|-------| | NotFound | 404 | Resource doesn't exist | | InvalidArgument | 400 | Bad input | | Unauthenticated | 401 | Missing/invalid auth | | PermissionDenied | 403 | Not allowed | | AlreadyExists | 409 | Duplicate resource |

Static Assets

Serve static files (HTML, CSS, JS, images) with api.static:

import { api } from "encore.dev/api";

// Serve files from ./assets under /static/*
export const assets = api.static(
  { expose: true, path: "/static/*path", dir: "./assets" }
);

// Serve at root (use !path for fallback routing)
export const frontend = api.static(
  { expose: true, path: "/!path", dir: "./dist" }
);

// Custom 404 page
export const app = api.static(
  { expose: true, path: "/!path", dir: "./public", notFound: "./404.html" }
);

Path Syntax

• *path - Standard wildcard: matches all paths under the prefix (e.g., /static/*path)
• !path - Fallback routing: serves static files at domain root without conflicting with other API endpoints. Use this for SPAs where unmatched routes should serve index.html

Guidelines

• Always use import not require
• Define explicit interfaces for type safety
• Use expose: true only for public endpoints
• Throw APIError instead of returning error objects
• For inbound webhooks (Stripe, GitHub, etc.) use api.raw — see the encore-webhook skill
• Path parameters are automatically extracted from the path pattern
• Use validation constraints (Min, MaxLen, etc.) for user input