vault-mcp-client

Local stdio↔HTTP MCP proxy for Iceberg Data's private vault-mcp service (hosted on a Mac Studio, reachable only over the Iceberg Tailnet).

Claude Code registers this binary as a stdio MCP server. On each tool call the proxy forwards the JSON-RPC message over HTTPS to the Tailnet URL, injecting a static bearer token on every request.

Install

pipx install vault-mcp-client

Requirements on the workstation:

• Logged into Tailscale as an Iceberg Data member.
• You have the shared bearer token (ask Julian — it's distributed out-of-band).

Register with Claude Code

claude mcp add vault vault-mcp-client \
  --scope user \
  -e VAULT_MCP_URL=https://mac-studio.tailXXXXXX.ts.net \
  -e VAULT_MCP_TOKEN=<bearer-token-from-julian>

Restart Claude Code → /mcp should show vault: ✓ Connected.

Verify

Ask Claude: "use server_info of the vault MCP". Expected response: the deploy metadata (version, repo root, auto-push flag, etc.).

Troubleshooting

• 401 Unauthorized: token mismatch. Confirm VAULT_MCP_TOKEN matches what the server has.
• Connection refused / timeout: you're not on the Iceberg Tailnet, or the Mac is offline. Run tailscale status and ping the Mac's Tailnet hostname.
• SSL / cert error: Tailscale handles certs via MagicDNS — if this pops up, your Tailscale client is outdated (brew upgrade tailscale or reinstall from the App Store).

Design notes

Auth is a static token because the vault-mcp server is single-tenant and reachable only inside the Tailnet. The audit trail lives in git (every write is a commit by vault-mcp-bot). If you need dynamic per-user auth later, swap the BearerAuth class in proxy.py for an OAuth/IAP-aware one.

Related: wse-dev-mcp-client is the sister package that talks to Iceberg's public Cloud Run MCP deploy using Google identity tokens instead of a static bearer.