Configuration[01]
Configuration
For the local server — npx -y @ontosdk/mcp, currently 1.5.2, on Node 20 or later. The remote connector needs none of this.
Build your config
[02]Version
mcpServers
{
"mcpServers": {
"onto": {
"command": "npx",
"args": ["-y", "@ontosdk/mcp@latest"],
"env": {
"ONTO_API_KEY": "onto_sk_live_YOUR_KEY"
}
}
}
}Keep the key in the env block, not the command line — some clients log their arguments. Without @latest, npx can keep reusing a copy it already downloaded.
What it reads
[03]VariableDefaultWhat it does
ONTO_API_KEYrequiredYour onto_sk_ key. Without it the server exits as it starts.ONTO_API_BASEhttps://api.buildonto.devWhere tool calls go. No trailing slash — it's joined straight onto each path.ONTO_NO_UPDATE_CHECKunsetAny value skips the npm lookup for a newer version. The one-time what's-new note still shows.It reads nothing else.
When it goes wrong
[04]You seeDo this
The tools never appearQuit the client fully, check the config is valid JSON (one trailing comma breaks it) and in the right file, then reopen.
The server exits straight awaySet
ONTO_API_KEY in the config's env.“Monthly plan quota exceeded and credit balance is empty”Out of credits for the month (402). Top up or upgrade on Billing.
“Onto API rate limit exceeded”Too many calls at once (429). Wait a moment — the local server doesn't retry for you.
A call gives up after 15 secondsThe page was too slow to answer. Try once more, then skip it.
Limits
[05]PlanCredits a monthCalls at once
Free1,0002
Starter10,0005
Growth100,00020
Scale500,00050