Send a GET to the rendering endpoint with a snippet name and JaaS returns the evaluated Jsonnet as JSON:

curl http://127.0.0.1:8080/jsonnet/example1

The Jsonnet server binds 127.0.0.1:8080 by default (--listen-address, --port). The URL shape is GET /<jsonnet-endpoint-path>/{snippet...}, where {snippet...} is a trailing path segment that may contain slashes. A successful response carries Content-Type: application/json and the rendered document.

The endpoint path

The leading path segment defaults to jsonnet and is set with --jsonnet-endpoint-path. Running with --jsonnet-endpoint-path render moves the endpoint to GET /render/{snippet...}:

./jaas --jsonnet-endpoint-path render --snippet-directory examples/snippets/dashboards
curl http://127.0.0.1:8080/render/example1

Snippet resolution

The {snippet...} segment names which file JaaS evaluates. Resolution checks the --snippet files first, then looks for <name>/main.jsonnet under each --snippet-directory. See Snippets and libraries for how to declare both.

Resolution is sandboxed through Go’s os.Root, which rejects .. traversal and symlinks that escape the configured directory. A crafted URL never reaches a file outside the snippet roots:

curl -i http://127.0.0.1:8080/jsonnet/../etc/passwd
# HTTP/1.1 404 Not Found

Management probes

A second HTTP server — the management server — exposes the Kubernetes lifecycle probes. It binds 127.0.0.1:8081 by default (--management-listen-address, --management-port):

A not-ready probe returns a JSON body naming the state:

curl -i http://127.0.0.1:8081/ready
# HTTP/1.1 503 Service Unavailable
# {"status":"not ready"}

Error contract

Every non-2xx response is an RFC 9457 problem document with Content-Type: application/problem+json so programmatic callers can pick the failure apart:

{
  "type":    "https://jaas.projects.metio.wtf/errors/snippet_not_found",
  "title":   "Snippet not found",
  "status":  404,
  "detail":  "snippet \"missing\" not found",
  "code":    "snippet_not_found",
  "snippet": "missing"
}

• type — the RFC 9457 problem-type URI, formed as https://jaas.projects.metio.wtf/errors/ + the code.
• title — a short, human-readable summary of the problem.
• status — the HTTP status, mirrored into the body.
• detail — human-readable specifics for this occurrence.
• code — the stable short identifier. Callers match on this; these strings do not change. It is the matcher that pairs with the type URI.
• snippet — echoes the requested name when one was parsed, and is omitted otherwise.

Error bodies use application/problem+json; a successful 200 response stays application/json and carries the rendered document.

For evaluation_failed, detail is the constant "evaluation failed". The full go-jsonnet diagnostic — syntax error, missing import, stack-limit, with file and line numbers — is written to the server logs instead of the response body, since it names on-disk snippet paths. Read the controller logs to debug a failing snippet; in operator mode the snippet’s failure also surfaces on its JsonnetSnippet status condition.

A client that closes the connection mid-evaluation receives no body and no status line — the handler detects the cancellation and returns without writing anything.

The timeout, stack, and concurrency caps that drive evaluation_timeout and evaluation_unavailable are documented in Evaluation and security . To pass values into a render, see External variables and TLAs .