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Devon Park
10 hours ago

Nightfall blocked a Gmail MCP send mid-draft

#agents#tooling#mcp
Nightfall MCP Gateway
Govern Cursor and Claude Code MCP tool calls

Tried Nightfall MCP Gateway this week after Cursor kept hitting our Gmail MCP with drafts.create in a loop.

First useful block was mid-reply — agent tried to send_message with a customer email still in the body. Policy caught it. Error in the tool log was something like NF_POLICY_DENY: outbound_pii.

Annoying part: the allowlist UI is very enterprise. Took me ~40 minutes to whitelist list_labels and nothing else. Worth it though. Anyone else running this in front of Claude Code, or just Cursor?

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  • Jake Ellison

    yeah i bounced off the sales call wall last month so this is interesting if there's a real solo path.

    did you pay anything or is it still trial? also curious if it logs the blocked payload — i don't want customer emails sitting in some security dashboard for 90 days.

    • Sara

      we keep a 2-hour break-glass for send_message during launch windows. permanent allow is how pii gets into a customer thread at 1am.

      if the audit log is on by default i'd want retention under 7 days for a two-person team. did anyone check whether blocked drafts still sit in gmail drafts.create?

  • Luna

    Running it in front of Claude Code here. Same story — needed allowlists on day one.

    One gotcha: if you deny Bash too aggressively the agent just retries with a slightly different tool name and burns tokens. I ended up allowing read-only shell and blocking anything that writes outside /tmp.

    Did Nightfall give you a per-tool deny reason in the Cursor UI, or only in their dashboard?

    • Loom Circuit

      Same on the retry burn. I logged three Bash aliases in one session before I pinned the schema.

      For the UI question: Cursor gave me only NF_POLICY_DENY plus the tool name. The human-readable reason (outbound_pii / path) was dashboard-only. If you cannot see tool name in the error, the gateway is basically opaque.

      Also: allowlist list_labels and forget get_message is a classic — agent looks "connected" and still cannot read threads.

  • Marcus Lee

    We put Nightfall in front of Gmail MCP last Tuesday after a near-miss send with a Stripe receipt still in the quote.

    Solo path exists but the UI is still "talk to sales" flavored. I paid the starter tier (~$49/mo) — it does log the blocked payload for 14 days by default. Turn that down if you care; retention is under Settings → Audit.

    Cursor only showed tool_error with the Nightfall code. The readable deny reason lived in their dashboard, same as you asked.

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