Draft: Tab MCP Slack Integration

[mattcfilbert]

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Description

Adds Slack integration support for tableau-mcp: documentation, validation tooling, and configuration
templates for connecting Tableau MCP to Slack apps via the mcp:connect scope.

Changes:

• Slack integration guide (docs/docs/extras/slack-integration.md) — Option A (passthrough/demo)
  and Option B (external auth/SSO) with Slack app manifest examples and Tableau Cloud DCR curl
• Validation script (scripts/validate-slack-mcp-flow.ts) — Staged MCP validator (handshake,
  discover, search, datasource, metadata, query, full) for passthrough-authenticated HTTP MCP. Parses
  SSE responses (text/event-stream), preserves mcp-session-id, supports VALIDATE_DEBUG for
  response inspection
• Demo env template (env.slack-demo.example) — Minimal env for Option A passthrough demo
• validate:slack-mcp npm script — Wires validator to npm run validate:slack-mcp
• env.example.list — Trimmed to essential vars (passthrough, HTTP, OAuth)
• OAuth docs — Updated Tableau Cloud wording to "currently limited" (removed ETA)
• .gitignore — Added .worktrees/

Motivation and Context

Enables customers and internal teams to connect Tableau MCP to Slack for Data Q&A-style workflows.
The validator proves local HTTP MCP connectivity and passthrough auth before integrating with Slack’s
runtime. Option A supports quick demos; Option B supports per-user OAuth when available.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Other (please describe):

How Has This Been Tested?

• Ran TABLEAU_SESSION_TOKEN='<token>' VALIDATE_STAGE=discover npm run validate:slack-mcp against
  local HTTP server with passthrough auth; handshake and discover succeed, 16 tools returned.
• Ran VALIDATE_STAGE=handshake in stateless mode (no session); handshake passes.
• All 921 unit tests pass (npm test).

Related Issues

Checklist

• I have updated the version in the package.json file by using npm run version. For example,
  use npm run version:patch for a patch version bump.
• I have made any necessary changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have documented any breaking changes in the PR description. For example, renaming a config
  environment variable or changing its default value.

Contributor Agreement

By submitting this pull request, I confirm that:

• I have read the CONTRIBUTING guidelines for this project and followed
  its Contribution Checklist.