Feature: Add `slack_update_draft` and `slack_delete_draft` MCP tools

[TomZaiger]

Summary

Please expose draft update and delete tools on the hosted Slack MCP server (https://mcp.slack.com/mcp), alongside the existing create path (slack_send_message_draft).

Today agents can create a draft for review, but cannot revise or discard it via MCP without either:

• asking the human to delete it in Slack Drafts & Sent, then creating again, or
• sending via slack_send_message with draft_id (deletes only as a side effect of sending).

Current surface

Capability	Tool
Create draft	slack_send_message_draft
Delete draft without sending	❌ none
Update draft text in place	❌ none
Delete draft after send	slack_send_message optional draft_id

Proposed tools

slack_update_draft

• Inputs: draft_id (required), message (required), optionally channel_id / thread_ts if needed for validation
• Behavior: Replace the body of an existing unsent draft; return the same draft_id + channel link
• Errors: draft_not_found, channel_not_found, auth failures

slack_delete_draft

• Inputs: draft_id (required), optionally channel_id
• Behavior: Discard an unsent draft without posting
• Errors: draft_not_found, auth failures

Motivation

Agent workflows routinely prepare a draft for human review, then iterate on wording before send. Without update/delete:

1. Duplicate creates are unsafe (see companion bug: false success when a draft already exists).
2. Humans must manually delete drafts in the Slack UI to unblock a rewrite.
3. The only MCP “delete” path forces sending (draft_id on slack_send_message).

Token / API note

Internal Slack client methods (drafts.update, drafts.delete, drafts.list) reportedly exist but may require client/session token types beyond standard OAuth user tokens used by the MCP. If that is the blocker, please document it on the create tool and keep create’s draft_already_exists behavior honest so agents do not silently no-op.

If OAuth can support update/delete, exposing them would close a large hole in the draft lifecycle for AI clients (Cursor, Claude Code, etc.).

Related

• Companion bug: slack_send_message_draft returns success when a draft already exists (should draft_already_exists)
• slack_send_message_draft strips newlines — draft renders as a single unbroken line #18 — draft newline stripping
• Feature precedent in this repo: other write-tool requests (e.g. status/DND tools)

Fix lives on the hosted MCP at mcp.slack.com; this repo is the public place to track it.

[vegeris]

Hi @TomZaiger,

Thank you for your feedback; this has been forwarded to the internal team

[JLLeitschuh]

It also looks like sending draft messages don't preserve the formatting. slack_send_message does support formatting

[m13v]

discard being the expensive operation and send being the cheap one is the tell here. the only mcp path that removes a draft is sending it, so every 'actually, no' costs a trip into slack's drafts ui, while 'ship it' stays a single call. approval gates drift toward approve whenever the exit door is the slow one.