---
title: "Build a sandbox image"
method: POST
path: "/projects/{projectId}/images/{imageId}/build"
tags: ["Sandbox images"]
---

# Build a sandbox image

`POST /projects/{projectId}/images/{imageId}/build`

Trigger a build of the sandbox image's image and respond `202`. The build runs asynchronously — poll the builds list for status. Bodyless. Guest callers are denied (a write).

## Path parameters

- `projectId` string, required
- `imageId` string, required

## Request body

- object

## Response `202`

The build was accepted.

- SandboxImageBuildStarted — A build was accepted (202). It runs in the background — poll the builds list for status.
  - `id` string, required — The sandbox image id.
  - `buildId` string, required
  - `reused` boolean, required — True when an identical prior build was reused instead of rebuilding.

## Other responses

- `400` — Malformed body or parameters.
- `401` — Missing, invalid, revoked, or orphaned key (`UNAUTHORIZED`) — or the **target MCP server** needs an OAuth grant (`OAUTH_REQUIRED`), which is a property of the server, not your key.
- `403` — Key is valid but not allowed to do this.
- `404` — Unknown project, server, or resource.
- `429` — Per-key rate limit exceeded (60 requests/minute sustained, bursts up to 10). Honor `Retry-After` and back off with jitter.
- `500` — Something failed on MCPJam's side.
- `502` — Could not connect to the target MCP server.

---

[API](https://skmtc.net/mcpjam/apis/mcpjam-api.md) · [All operations](https://skmtc.net/mcpjam/apis/mcpjam-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/mcpjam/mcpjam-api/versions/75f218486b1d/schema)