---
title: Constants and prompts
description: Declare shared values with defineConstants and definePrompt, and understand how context resolution works.
pagination: false
sidebar:
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---

Use `defineConstants` for named JSON values, environment references, or resolver functions.
Use `definePrompt` for nonempty text or an ordered list of text fragments. Both APIs create
immutable descriptors; they do not read the environment or call a model during construction.

## Scaffold shared values

From an installed application's root, with an existing `orders` service, create the values you need:

```sh title="Terminal — application root"
bun run relkit add constants receipt-settings --service orders
bun run relkit add prompt receipt-policy --service orders \
  --text "Summarize the receipt."
```

The commands create `src/services/orders/constants/receipt-settings.constants.ts` and
`src/services/orders/prompts/receipt-policy.prompt.ts`. Constants start with a domain-qualified
key and a `"replace-me"` value; edit that value in source. Repeated `--text` flags preserve
separate prompt segments. Neither artifact becomes a public service member.

Use `--create-service orders` instead of `--service orders` if the service does not exist.
To create both artifacts, create the service with the first command and use `--service orders`
for the second. For manual setup, define the same descriptors in source as shown below.

See the [constants command](/docs/api/cli#relkit-add-constants-name) and
[prompt command](/docs/api/cli#relkit-add-prompt-name) for all flags, then
[use a prompt in an agent](/docs/modules/ai/agents#scaffold-a-reusable-prompt).

## Define shared values

> **Before you begin**
>
> Start with an [existing RELKIT application](/docs/learn/create-an-app), which already has
> `@relkit/app`. Declare these values alongside its service code:

```ts title="src/services/orders/context-values.ts"
/** Declares shared context values and resolves them without starting an HTTP server or model. */
import {
  createApplicationContextResolver,
  defineConstants,
  defineEnv,
  definePrompt,
  env,
} from "@relkit/app";

const environment = defineEnv({ REGION: env.string() });
export const limits = defineConstants(
  { maxItems: 20, region: environment.REGION },
  { id: "orders.constants" },
);
export const supportPrompt = definePrompt(
  ["Answer using the order details.", "Do not invent delivery dates."],
  { id: "support.prompt" },
);

export const contextResolver = createApplicationContextResolver({
  env: { REGION: "eu-west-1" },
  constants: { orders: limits },
  prompts: { support: supportPrompt },
});
```

`limits` declares `maxItems` and a typed environment reference. `supportPrompt` keeps its
two text fragments in order. The explicit IDs remain stable if you move or rename the file.
For environment parsing and defaults, read [Environment contracts](/docs/learn/concepts/environment).

## Resolve the context

The example also constructs `createApplicationContextResolver` for a caller that owns context
resolution. Call its `resolve` method with a logger and cancellation signal. It returns
`constants.maxItems` as `20`, `constants.region` as `"eu-west-1"`, and
`prompts.support` as the two text fragments.

Static values are prepared when the resolver is created. Function-valued constants run on
each resolution and receive the environment, logger, and cancellation signal. Duplicate
constant names across registered descriptors are rejected. These are context-resolution APIs;
`defineApp` does not accept `constants` or `prompts` configuration properties.

See [`defineConstants`](/docs/api/app#defineconstants), [`definePrompt`](/docs/api/app#defineprompt),
and [`createApplicationContextResolver`](/docs/api/app#createapplicationcontextresolver) for
their exact contracts. Continue with [Invocation context](/docs/learn/concepts/context) or
[Build an offline agent](/guides/ai/build-an-offline-agent).

{/* Generated by apps/docs/scripts/generate.ts. Do not edit. */}

**Reference and source**

- [`@relkit/app` API](/docs/api/app)
- [`@relkit/config` API](/docs/api/config)

- [`apps/docs/examples/public-api/context.ts`](https://github.com/rel-kit/relkit/blob/main/apps/docs/examples/public-api/context.ts)