---
title: "Validate a blueprint"
method: POST
path: "/projects/{projectId}/images/validate"
tags: ["Sandbox images"]
---

# Validate a blueprint

`POST /projects/{projectId}/images/validate`

Lint blueprint YAML without saving it. Returns 200 with `ok: false` + structured errors for an invalid blueprint; the authoritative rejection still happens at create/update/build.

## Path parameters

- `projectId` string, required

## Request body

- SandboxImageBlueprintValidateRequest
  - `blueprint` string, required — Blueprint YAML to lint.

## Response `200`

Lint result

- union — Lint result. `ok: true` carries the resolved base digest; `ok: false` carries structured errors. Always returned with HTTP 200 — an invalid blueprint is a successful lint.
  - object
    - `ok` true, required
    - `baseImageDigest` string, required — Resolved sha256 digest of `base` (present when ok).
    - `errors` object[]
      - `path` string, required — Location of the violation, e.g. `initialize[0].run` (empty for document-level errors).
      - `message` string, required
  - object
    - `ok` false, required
    - `baseImageDigest` string — Resolved sha256 digest of `base` (present when ok).
    - `errors` object[], required
      - `path` string, required — Location of the violation, e.g. `initialize[0].run` (empty for document-level errors).
      - `message` string, required

## 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/b767df188d0c/schema)