> ## Documentation Index > Fetch the complete documentation index at: https://docs.ornn.com/llms.txt > Use this file to discover all available pages before exploring further. # Get a listing's free capacity > Returns how many of a listing's GPUs, and on how many nodes, are free to book over time, from now (or the listing's start) until the listing ends, or 30 days ahead when it has no end. Use it to choose a window before you book or offer. GPUs running Spot VMs count as free, because a booking ends Spot on its GPUs when it starts. Reserve listings return 404 unless your organization is approved or owns the listing. See [Buy relisted capacity](/guides/secondary-market.md#use-the-api) for the complete purchase flow. ## OpenAPI ````yaml openapi.yaml GET /v1/markets/listings/{listingId}/availability openapi: 3.1.0 info: title: Ornn compute API version: 1.0.0 description: >- Customer HTTP API for Ornn GPU capacity. It covers reserved capacity and nodes, VM and Bare Metal access, Kubernetes and Slurm clusters, SSH keys, storage volumes and GitHub repositories, private networks, monitoring, buying and selling capacity (Reserve, Market, order books, and Relist), and billing. API keys are scoped to one organization and act with their creator's access there; account, team, and API-key management stay in the console. Most operations require an approved organization. See https://docs.ornn.com/api-keys to create a key and https://docs.ornn.com/guides/kubernetes-api for an end-to-end Kubernetes integration. Examples use fictional IDs and credentials. The info.version field identifies the contract revision, not a shared API path version. contact: email: support@ornn.com servers: - url: https://api.ornn.com description: Production security: - OrnnApiKey: [] tags: - name: Authentication - name: Reservations - name: GPU nodes - name: Clusters - name: Workers - name: Virtual machines description: >- Choose a VM disk, launch VM access on a reservation, and read each VM's status, launch progress, and SSH connection details. - name: Bare Metal description: >- Launch Bare Metal access on a reservation, read a host's readiness and SSH connection details, and reboot or hard reset it. - name: SSH keys description: >- Register public keys for your organization, choose which keys a VM or Bare Metal reservation uses, and queue key delivery to machines. Slurm clusters take organization key IDs at launch. Kubernetes API access does not use SSH keys. - name: Reserve description: >- Browse reserved-capacity listings and their terms, and post, cancel, or accept offers. Reserve listings are visible to approved organizations. - name: Market description: >- Browse relisted capacity and buy windows at the asking price, paid up front. Open to every member of your organization. - name: Order books description: >- Hourly order books for whole nodes, one VM per node: read books, trades, and quotes, place and cancel bids, and follow and end fills. - name: Relist description: >- Sell whole nodes from a reservation you hold at your asking price, and manage those listings. - name: Storage description: >- Managed volumes, their files, and GitHub repository pulls. Volumes belong to the API key's creator in the key's organization. - name: Networks description: >- Organization private networks and the WireGuard configs you use to reach private machines and clusters. - name: Monitoring description: >- Machine telemetry and console logs for capacity your organization holds. Reads are limited to your reservation window. - name: Billing description: >- Invoices, billing summary, usage cost, Ornn credits, and account statements. Saving a card and paying invoices stay in the console. externalDocs: description: REST integration walkthrough url: >- https://docs.ornn.com/guides/kubernetes-access#provision-and-manage-through-rest paths: /v1/markets/listings/{listingId}/availability: get: tags: - Market - Reserve summary: Get a listing's free capacity description: >- Returns how many of a listing's GPUs, and on how many nodes, are free to book over time, from now (or the listing's start) until the listing ends, or 30 days ahead when it has no end. Use it to choose a window before you book or offer. GPUs running Spot VMs count as free, because a booking ends Spot on its GPUs when it starts. Reserve listings return 404 unless your organization is approved or owns the listing. operationId: capacityGetAvailability parameters: - name: listingId in: path required: true description: Listing ID (capacityListingId or listingId). schema: type: string format: uuid example: 77777777-7777-4777-8777-777777777777 - name: from in: query required: false description: RFC 3339 time. Start no earlier than this. schema: type: string format: date-time example: '2026-10-20T00:00:00Z' - name: to in: query required: false description: RFC 3339 time. End no later than this. schema: type: string format: date-time example: '2026-11-20T00:00:00Z' responses: '200': description: >- Free GPUs per interval, and the nodes they are on. Adjacent intervals with the same counts are merged. content: application/json: schema: $ref: '#/components/schemas/CapacityAvailability' example: listingId: 77777777-7777-4777-8777-777777777777 windows: - startsAt: '2026-10-20T00:00:00Z' endsAt: '2026-10-21T00:00:00Z' gpus: 16 nodes: 2 - startsAt: '2026-10-21T00:00:00Z' endsAt: '2026-10-23T00:00:00Z' gpus: 12 nodes: 1 - startsAt: '2026-10-23T00:00:00Z' endsAt: '2026-11-03T00:00:00Z' gpus: 16 nodes: 2 '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '404': description: The listing does not exist or is not visible to your organization. content: application/json: schema: $ref: '#/components/schemas/Error' example: detail: code: listing_not_found message: Ornn could not find that listing. '422': description: An invalid time, or to is not after from. content: application/json: schema: $ref: '#/components/schemas/Error' example: detail: code: invalid_window message: Choose a window that ends after it starts, in whole seconds. default: $ref: '#/components/responses/Error' components: schemas: CapacityAvailability: type: object required: - listingId - windows properties: listingId: type: string format: uuid windows: type: array description: Free capacity over time, in order. items: $ref: '#/components/schemas/CapacityAvailabilityWindow' Error: type: object properties: code: type: string detail: oneOf: - type: string - type: object required: - code - message properties: code: type: string message: type: string CapacityAvailabilityWindow: type: object required: - startsAt - endsAt - gpus - nodes properties: startsAt: type: string format: date-time endsAt: type: string format: date-time gpus: type: integer description: GPUs free for this whole interval. nodes: type: integer description: Nodes with at least one GPU free for this whole interval. responses: Unauthorized: description: >- The credential is missing, invalid, revoked, or no longer belongs to a current organization member. Check the HTTP status before parsing the body. content: application/json: schema: $ref: '#/components/schemas/Error' Forbidden: description: >- The credential lacks access to this operation, or the organization requires approval. An API key does not bypass these checks. content: application/json: schema: $ref: '#/components/schemas/Error' Error: description: >- Unsuccessful request. Check HTTP status first. Errors may have detail.code/detail.message, a string detail and optional top-level code, or an empty/non-JSON body. 401: invalid credential; 403: access or approval required; 404: not visible or credentials not ready; 409: lifecycle conflict; 429: back off; 5xx: service failure. Inspect current state before retrying mutations. content: application/json: schema: $ref: '#/components/schemas/Error' securitySchemes: OrnnApiKey: type: http scheme: bearer bearerFormat: ornn_sk_... description: >- Create an organization API key in Account Settings > Developer. Do not send this key to the Kubernetes API server. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.