MCP serverRemote connector (OAuth)
API reference llms.txt
Docs›MCP Server›Remote connector
Remote connector[01]

Remote connector (OAuth)

One URL — https://api.buildonto.dev/mcp — and a sign-in with your Onto account. No key to paste, nothing to install.

What connecting does

[02]
your client ⇄ api.buildonto.dev
You add https://api.buildonto.dev/mcp

  1. In your client's connector settings — or with one command in Claude Code and Codex.

  2. Its first call is refused with a 401 pointing at api.buildonto.dev's own OAuth metadata. The client registers itself there.

  3. You sign in to your Onto account on app.buildonto.dev and allow the client. That's the only step that needs you.

  4. The client swaps a one-time code (PKCE, S256) for an access token that lasts an hour and a refresh token that lasts 30 days, and renews them itself.

  5. The same six tools as the local server, calling the same endpoints.

Six tools in your client, billed to your account

Connect your client

[03]

Claude, Claude Code, Cursor, Codex and ChatGPT all connect by URL. Pick yours for the exact place it goes:

Install in
One command
$ claude mcp add --scope user --transport http onto https://api.buildonto.dev/mcp
Docs →
  1. Run it in a terminal. Claude Code asks you to approve Onto on first use.
  2. Then ask Claude Code to “read example.com with onto”.

How sign-in works

[04]
What it is
Authorization serverhttps://api.buildonto.dev — Onto's own; no third party
Endpoints/authorize, /token, /register (dynamic client registration), /revoke
SecurityPKCE with S256 is required; the access token is bound to the /mcp resource
Scopeonto:read
TokensAccess: 1 hour. Refresh: 30 days, used once and replaced each time
Or a key/mcp also takes an onto_sk_ API key as the Bearer token

Test it with the Inspector

[05]

To watch the whole flow — the 401, the sign-in, the tools — run the official MCP Inspector, set the transport to Streamable HTTP, paste the URL and connect:

npx @modelcontextprotocol/inspector

Then list the tools and call read_url with { "url": "https://stripe.com/pricing" }.

Remote or local

[06]
Remote connectorLocal server
TransportStreamable HTTP at /mcp (SSE at /sse)stdio, via npx
Signs in withYour Onto account, over OAuthAn onto_sk_ key in ONTO_API_KEY
SetupPaste one URL, approveA config block, then restart
Tools and billingSame six, same creditsSame six, same credits