> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kvant.sbs/jeston/llms.txt
> Use this file to discover all available pages before exploring further.

# API routes

# API routes

***

## Core · API routes

> **Core principle** — Make every endpoint a small, observable protocol rather than an arbitrary function behind a URL.

Stable methods, input validation, status codes, headers, errors, and cancellation.

### Key concepts

<Columns cols={3}>
  <Card title="Malformed JSON" icon="sparkles">
    400
  </Card>

  <Card title="Unauthorized" icon="shield-check">
    401
  </Card>

  <Card title="Forbidden" icon="gauge-high">
    403
  </Card>
</Columns>

### Boundary model

```mermaid placement="top-right" theme={null}
flowchart LR
    request[Method and body] --> validate[Validate input]
    validate --> authorize[Authorize]
    authorize --> domain[Domain operation]
    domain --> response[Status headers body]
```

### Ownership matrix

| Concern            | Jeston/application boundary | Review signal                                 |
| ------------------ | --------------------------- | --------------------------------------------- |
| Malformed JSON     | 400                         | No domain side effect.                        |
| Unauthorized       | 401                         | Identity is absent or invalid.                |
| Forbidden          | 403                         | Identity exists but policy denies.            |
| Dependency failure | 5xx                         | Safe public body and correlated internal log. |

### Engineering considerations

A clear HTTP contract lets clients, tests, proxies, and operators reason about behavior independently.

> **Design constraint**
>
> An API is a promise about failure as much as it is a promise about success.

### Implementation notes

| Engineering move             | Guidance                                                                           |
| ---------------------------- | ---------------------------------------------------------------------------------- |
| **Choose the method**        | Align semantics with read, create, replace, partial update, or delete behavior.    |
| **Validate before work**     | Return a stable 400 shape for malformed JSON or invalid fields.                    |
| **Set status intentionally** | Do not make clients infer success from a generic 200 response.                     |
| **Bound the handler**        | Use deadlines, signals, body limits, and idempotency where repetition is possible. |

### Decision lens

| Mode       | Practical emphasis                                               |
| ---------- | ---------------------------------------------------------------- |
| **Read**   | Cache only when freshness and authorization semantics are clear. |
| **Write**  | Make retries safe with idempotency or explicit non-retry policy. |
| **Stream** | Define event framing, disconnect behavior, and terminal state.   |

## Related topics

<Columns cols={3}>
  * [globe · **Read HTTP semantics**](/jeston/jeston/reference/http-contracts) — Read the focused guide for this boundary.
  * [shield-halved · **Harden boundaries**](/jeston/jeston/platform/security) — Read the focused guide for this boundary.
  * [chart-line · **Expose signals**](/jeston/jeston/platform/health-observability) — Read the focused guide for this boundary.
</Columns>

## References

[1]: https://github.com/jeffersoncampos12p-dev/jeston "Jeston source repository"

[2]: https://www.npmjs.com/package/@kvantjs/jeston "Jeston package on npm"

[3]: https://nodejs.org/api/http.html "Node.js HTTP API"

[4]: https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal "AbortSignal Web API"

[5]: https://react.dev/reference/react-dom/server "React server rendering APIs"

[6]: https://www.typescriptlang.org/docs/handbook/intro.html "TypeScript handbook"