Draft/preview mode for Slack MCP conversations_add_message?

Question

Does korotovsky/slack-mcp-server support a draft or preview mode for conversations_add_message? An agent-written message posts immediately with no review, which is risky if the generated text contains errors or prompt-injected content. As of May 2026, what options exist to get human approval before a message is sent?

Originally asked on GitHub: https://github.com/korotovsky/slack-mcp-server/issues/246

AgentArmorHQ team · Accepted Answer

The feature request is still open as of the last comment (May 2026): `conversations_add_message` posts immediately and the server has no draft, preview, or dry-run mechanism. The thread does not discuss releases, so no version information is available.

A pull request (#248) was opened to address this by adding a separate `conversations_draft_message` tool rather than a `dry_run` parameter on the existing tool. Keeping it separate means it can be annotated `readOnlyHint: true` and `destructiveHint: false`, so MCP clients can treat a preview call differently from a write operation (for example, showing it without a confirmation prompt). The thread never states whether the PR was merged, so assume it is not available until you verify.

Two workarounds are mentioned in the thread:
- Rely on the agent host's permission prompt before tool execution. This only shows the raw tool parameters, not a formatted message preview.
- Run a second Slack MCP server (the Anthropic-built one, which includes `slack_send_message_draft`) alongside this one, just for draft/send flows. The thread calls this clunky but does not evaluate whether it works.

The thread also references issue #235, which flagged the immediate-send behavior of `PostMessageContext` as a HIGH finding (no confirmation, dry-run, or draft mechanism). If you need human review of agent-written messages, follow #248 or the original issue for updates.

Draft/preview mode for Slack MCP conversations_add_message?

1 answer