# Create domains URL: https://docs.hanzo.ai/docs/openapi/platform/post-platform-projects-by-project-apps-by-app-domains > Attaches a hostname — instantly if you already own it, otherwise with a DNS challenge. `POST /v1/platform/projects/{project}/apps/{app}/domains` > [Platform →](https://docs.hanzo.ai/docs/openapi/platform) · [All API references →](https://docs.hanzo.ai/docs/openapi) · [Get started →](https://docs.hanzo.ai/docs/guides) | | | | ------------- | ------------------------------------------------------------------------ | | **Address** | `https://api.hanzo.ai/v1/platform/projects/{project}/apps/{app}/domains` | | **Method** | `POST` | | **Operation** | `post_platform_projects_by_project_apps_by_app_domains` | | **Auth** | `Authorization: Bearer $HANZO_API_KEY` | Attaches a hostname — instantly if you already own it, otherwise with a DNS challenge. It attaches `host` to the app, and which of two things happens depends on who owns the name. A host inside the caller org's own subtree is structurally owned, so it goes ACTIVE immediately and answers 201. A bring-your-own host is claimed as PENDING and answers the DNS challenge records to publish; it is NOT rendered into the app's ingress until /verify passes. Claims are globally unique. A host already claimed by another organization is 409, and so is one claimed by a different app in your own; re-adding this app's OWN claim is idempotent and answers its current state at 200. The default host is always attached and re-adding it is 409. A host under the platform's shared apex that is not the caller's own subtree is 403 — it belongs to whoever owns that subtree and can never be grabbed through the custom path. `host` must be a valid DNS hostname; anything else is 400. Requires a validated principal; 401 without one. ## Request 5 fields, body `application/json` (required). | Field | In | Type | Required | Description | | --------- | ---- | ------ | -------- | ------------------------------------------------------------------ | | `project` | path | string | yes | Project is the project the application lives under, from the path. | | `app` | path | string | yes | App is the application's slug, from the path. | | `app` | body | string | — | App is the application's slug, from the path. | | `host` | body | string | — | Host is the hostname to attach. | | `project` | body | string | — | Project is the project the application lives under, from the path. | ## Response | Status | Body | Meaning | | --------- | ------------------- | ------- | | `200` | platform.domainView | ok | | `201` | platform.domainView | created | | `default` | problem-details | refused | `200` body — 12 fields. | Field | In | Type | Always | Description | | ----------------- | ---- | ------------------ | ------ | ------------------------------------------------------------------------------------------------------------------- | | `createdAt` | body | integer (int64) | — | CreatedAt is the unix second the custom claim was made. | | `detail` | body | string | — | Detail says why a claim is still pending, in the resolver's own words. | | `host` | body | string | — | Host is the hostname itself. | | `kind` | body | string | — | Kind is `default`, `subtree` or `custom` — how the org came to own it. | | `primary` | body | boolean | — | Primary marks the app's permanent default host. | | `records` | body | platform.Record\[] | — | Records are the DNS records to publish while a custom claim is pending. | | `records[].name` | body | string | — | the record name the customer creates | | `records[].type` | body | string | — | TXT \| CNAME | | `records[].value` | body | string | — | the record value | | `status` | body | string | — | Status is `live`, `provisioning`, `pending_deploy` or `pending`, derived from the operator CR and never fabricated. | | `url` | body | string | — | URL is the host as an HTTPS address. | | `verified` | body | boolean | — | Verified is whether ownership is settled — always true for a host the org structurally owns. | Failure carries the platform error shape — see [Errors](https://docs.hanzo.ai/docs/errors). ## Examples **CLI** ```bash hanzo platform projects apps domains create ``` **SDK** **.ts** ```ts import { Configuration, PlatformApi } from 'hanzoai'; const api = new PlatformApi(new Configuration({ accessToken: process.env.HANZO_API_KEY })); const { data } = await api.postPlatformProjectsByProjectAppsByAppDomains({ project: 'project', app: 'app', app: "", host: "" }); ``` **.py** ```python from hanzoai.cloud import ApiClient, Configuration from hanzoai.cloud.api import PlatformApi client = ApiClient(Configuration(access_token=os.environ["HANZO_API_KEY"])) result = PlatformApi(client).post_platform_projects_by_project_apps_by_app_domains(project='project', app='app', app="", host="") ``` **.go** ```go cfg := hanzoai.NewConfiguration() cfg.AddDefaultHeader("Authorization", "Bearer "+os.Getenv("HANZO_API_KEY")) client := hanzoai.NewAPIClient(cfg) resp, _, err := client.PlatformAPI.PostPlatformProjectsByProjectAppsByAppDomains(context.Background()).Execute() if err != nil { return err } ``` **.rs** ```rust use hanzo_client::apis::{configuration::Configuration, platform_api}; let mut cfg = Configuration::new(); cfg.bearer_access_token = std::env::var("HANZO_API_KEY").ok(); let result = platform_api::post_platform_projects_by_project_apps_by_app_domains(&cfg, Default::default()).await?; ``` **.java** ```java import ai.hanzo.cloud.ApiClient; import ai.hanzo.cloud.api.PlatformApi; ApiClient client = new ApiClient(); client.setBearerToken(System.getenv("HANZO_API_KEY")); var result = new PlatformApi(client).postPlatformProjectsByProjectAppsByAppDomains(); ``` **HTTP** ```bash curl -X POST https://api.hanzo.ai/v1/platform/projects//apps//domains \ -H "Authorization: Bearer $HANZO_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "app": "", "host": "" }' ``` **MCP** MCP reaches **platform** through the `platform` tool, which names its 38 operations with its own verbs — this one among them, under a name only MCP declares. `describe` explains any of them: ```bash curl -X POST https://api.hanzo.ai/v1/mcp \ -H "Content-Type: application/json" \ -d '{ "jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": { "name": "describe", "arguments": { "op": "get_build" } } }' ``` --- [Platform API](https://docs.hanzo.ai/docs/openapi/platform) · [All Hanzo APIs](https://docs.hanzo.ai/docs/openapi) · [Interactive reference](https://docs.hanzo.ai/docs/openapi/reference)