The Onyx Connector

Connect Claude — or any MCP client — to your own Onyx server · self-hosted · setup & usage

The connector links an MCP client to your Onyx deployment. Policies, requests, decisions, certificates, and the audit trail all live on your infrastructure — nothing routes through The Onyx Foundry. See the privacy policy.

What you need

An Onyx server you operate, with its MCP endpoint enabled — the Onyx gateway serves MCP over Streamable HTTP at POST /mcp.
An HTTPS URL for that endpoint, reachable from your MCP client.
Authentication appropriate to your deployment: run the endpoint behind your network controls or authenticating proxy. Do not expose an unauthenticated endpoint to the public internet.

Connecting from Claude

Start your Onyx gateway with the MCP transport enabled and note its HTTPS URL.
In Claude, open Settings → Connectors → Add custom connector and enter your server's URL.
Ask Claude to use an Onyx tool — for example one of the prompts below. Decisions and verifications run on your server; results, certificates, and trail records stay there.

Tools

Gating tools decide an action and append a record to the hash-chained audit trail; verification and audit tools are read-only.

Tool	Does	Access
gate_action	Decide one authorization request against your policy set — fail-closed, with the decision proved.	writes trail
gate_tool_call	Decide whether an agent tool call may proceed — the runtime gate for agent stacks.	writes trail
gate_transaction	Decide a custody-style transaction (ordered rules, first match, quorum approvals) with the quorum report.	writes trail
verify_policies	Verify assert/obligate properties over all requests — counterexamples on violation, certificates on pass.	read-only
verify_tx_policy	Verify custody-policy safety properties (e.g. no single signer) with witness transactions and a certificate bundle.	read-only
verify_claim	Prove or refute premises ⊢ conjecture; a non-theorem returns a concrete countermodel.	read-only
check_smt	Decide satisfiability over the built-in theories; every unsatisfiable answer carries a re-checkable certificate.	read-only
audit_proof	Step-by-step audit of an external prover's proof (TSTP or Alethe format), verdict per step.	read-only

Example prompts

"Before running this transfer, gate it against our treasury policy."
"Can any request from the contractors group ever reach the production database under these policies? Prove it or show me a counterexample."
"Audit this solver proof and tell me which steps verify."

Data handling

The connector reads (verifications, proofs, audits) and writes (audit-trail records from gating decisions) — entirely on your server. Onyx decides whether actions and transactions comply with your declared policy; it never initiates or executes transactions or moves funds.

Support

contact@onyxfoundry.ai · security reports: security.txt