---
# @generated by sylphx-gen 0.1.0 from contracts@190f1b33b937c1aef79697684018db853389b521c75e19ff69ac6af609e96f45. Do not edit.
title: "Create an usage reservation"
description: "`money.usage_reservations.create` (POST /v1/{parent}/usage_reservations): Reserves usage before the work starts."
type: reference
product: payments
summary: "Reserves usage before the work starts."
updated: 2026-09-28
nav: false
---

Reserves usage before the work starts. Refused with PLAN_LIMIT_REACHED (spend limit, no payment method) or INVALID_STATE (suspended) only while enforcement is on; while it is dark the reservation is granted and the refusal is recorded.

- **Path** `POST https://api.sylphx.com/v1/orgs/acme/projects/shop/envs/production/usage_reservations`
- **Scope** `billing:metering:write`
- **Effect** `write` — a successful call changes state.
- **Collection** [usage_reservations](/docs/api/usage_reservations)

## Request

| Field | Type | What it is |
| --- | --- | --- |
| `parent` | `string` | The environment to create in. Required. |
| `usage_reservation` | `UsageReservation` | The reservation. Required. |

### UsageReservation

| Field | Type | What it is |
| --- | --- | --- |
| `name` | `string` | `orgs/{org}/projects/{project}/envs/{env}/usage_reservations/{usage_reservation}`. |
| `meta` | `ResourceMeta` | Resource metadata. |
| `subject` | `Subject` | Who uses it. Required. |
| `subject_proof` | `string` | The acting end user's access token, required on every reserve: Money proves the subject itself, fresh, with the caller's own key (`auth:sessions:verify`) or the merchant's configured issuer. Never stored. A raw id is refused with PERMISSION_DENIED (reason `subject_unverified`). Required. |
| `actor_proof` | `string` | For a customer organization: the token of the acting user, whose membership of the organization is checked fresh. The subject is Sylphx Auth's bare organization id (`acme`), never a resource name. Never stored. |
| `meter` | `string` | The meter's lookup key. Required. |
| `max_quantity` | `int64` | The most the work may use, in the meter's base unit. Required. |
| `ttl` | `duration` | How long the hold lasts, at most `600s`; default `600s`. |

### ResourceMeta

| Field | Type | What it is |
| --- | --- | --- |
| `labels` | `map<string, string>` | Caller-writable, indexed labels (AIP-122 label rules). |
| `annotations` | `map<string, string>` | Caller-writable, unindexed annotations. |
| `display_name` | `string` | Caller-writable human-readable name. |

### Subject

| Field | Type | What it is |
| --- | --- | --- |
| `end_user` | `string` | An end user's id (Sylphx Auth, or the app's own OIDC issuer). One of the `kind` group. |
| `customer_organization` | `string` | A customer organization's id. One of the `kind` group. |

## Response

| Field | Type | What it is |
| --- | --- | --- |
| `name` | `string` | `orgs/{org}/projects/{project}/envs/{env}/usage_reservations/{usage_reservation}`. |
| `uid` | `string` | `ures_<cell><ulid>`; never reused. Output only. |
| `meta` | `ResourceMeta` | Resource metadata. |
| `subject` | `Subject` | Who uses it. Required. |
| `subject_proof` | `string` | The acting end user's access token, required on every reserve: Money proves the subject itself, fresh, with the caller's own key (`auth:sessions:verify`) or the merchant's configured issuer. Never stored. A raw id is refused with PERMISSION_DENIED (reason `subject_unverified`). Required. |
| `actor_proof` | `string` | For a customer organization: the token of the acting user, whose membership of the organization is checked fresh. The subject is Sylphx Auth's bare organization id (`acme`), never a resource name. Never stored. |
| `meter` | `string` | The meter's lookup key. Required. |
| `max_quantity` | `int64` | The most the work may use, in the meter's base unit. Required. |
| `ttl` | `duration` | How long the hold lasts, at most `600s`; default `600s`. |
| `granted_quantity` | `int64` | What was granted: at most `max_quantity`, less under headroom. Output only. |
| `state` | `string` | `held`, `settled`, or `released`. Output only. |
| `expire_time` | `timestamp` | When the hold ends. Output only. |
| `dark_refusal` | `string` | While enforcement is dark: why it would have been refused (`spend_limit_reached`, `no_payment_method`, `account_suspended`); empty otherwise. Output only. |

### ResourceMeta

| Field | Type | What it is |
| --- | --- | --- |
| `generation` | `int64` | Increases by one on every change to `spec`. Output only. |
| `etag` | `string` | Strong ETag (AIP-154): changes on any change to spec, status, or metadata. Send it back as `If-Match` or `etag` to make Update and Delete conditional; a mismatch fails with ABORTED / 409 `ETAG_MISMATCH`. Output only. |
| `create_time` | `timestamp` | When the Resource was created. Output only. |
| `update_time` | `timestamp` | When the Resource last changed. Output only. |
| `delete_time` | `timestamp` | Set while the Resource is being deleted. Output only. |
| `labels` | `map<string, string>` | Caller-writable, indexed labels (AIP-122 label rules). |
| `annotations` | `map<string, string>` | Caller-writable, unindexed annotations. |
| `display_name` | `string` | Caller-writable human-readable name. |
| `creator` | `string` | The principal that created the Resource. Output only. |

### Subject

| Field | Type | What it is |
| --- | --- | --- |
| `end_user` | `string` | An end user's id (Sylphx Auth, or the app's own OIDC issuer). One of the `kind` group. |
| `customer_organization` | `string` | A customer organization's id. One of the `kind` group. |

## Errors

- [`UNAUTHENTICATED`](/docs/api/errors/UNAUTHENTICATED) — No valid key or token was presented.
- [`PERMISSION_DENIED`](/docs/api/errors/PERMISSION_DENIED) — The key lacks the method's permission.
- [`INVALID_FIELD`](/docs/api/errors/INVALID_FIELD) — A field failed validation.
- [`UNKNOWN_FIELD`](/docs/api/errors/UNKNOWN_FIELD) — The request has a field the schema does not know.
- [`INVALID_STATE`](/docs/api/errors/INVALID_STATE) — The Resource is in a state that forbids the call.
- [`PLAN_LIMIT_REACHED`](/docs/api/errors/PLAN_LIMIT_REACHED) — The plan's limit is reached.
- [`IDEMPOTENCY_KEY_REUSED`](/docs/api/errors/IDEMPOTENCY_KEY_REUSED) — An Idempotency-Key was reused with another body.
- [`IDEMPOTENCY_IN_PROGRESS`](/docs/api/errors/IDEMPOTENCY_IN_PROGRESS) — The first call with this Idempotency-Key is still running.
- [`UNAVAILABLE`](/docs/api/errors/UNAVAILABLE) — The Resource store, the owning service's backend, or the key verifier's snapshot is unavailable; retry after Retry-After.

Every error arrives in the body [Errors](/docs/platform/errors) describes.

## Examples

**cURL**

```curl
curl -X POST "https://api.sylphx.com/v1/orgs/acme/projects/shop/envs/production/usage_reservations" \
  -H "Authorization: Bearer $SYLPHX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"max_quantity":1,"meter":"…","subject":{},"subject_proof":"…"}'
```

**TypeScript**

```ts
const response = await sylphx.money.usageReservations.create({ parent: 'orgs/acme/projects/shop/envs/production', usageReservation: { maxQuantity: 1, meter: '…', subject: {}, subjectProof: '…' } })
```

**Rust**

```rust
let mut req = sylphx::money::CreateUsageReservationRequest::default();
req.parent = "orgs/acme/projects/shop/envs/production".to_string();
req.usage_reservation = Some(sylphx::money::UsageReservation {
    max_quantity: 1,
    meter: "…".to_string(),
    subject: Some(Default::default()),
    subject_proof: "…".to_string(),
    ..Default::default()
});
let response = sx.money().usage_reservations().create(req).await?;
```

**CLI**

```bash
sylphx money usage-reservations create --parent orgs/acme/projects/shop/envs/production --subject-proof … --meter … --max-quantity 1
```

**MCP**

```json
{ "method_id": "money.usage_reservations.create", "args": {"parent":"orgs/acme/projects/shop/envs/production","usage_reservation":{"max_quantity":1,"meter":"…","subject":{},"subject_proof":"…"}} }
```