Slack Openapi Skill

Slack Web API Skill

Use this skill to run Slack Web API operations through uxc + OpenAPI.

Reuse the uxc skill for shared execution, auth, and error-handling guidance.

Prerequisites

• uxc is installed and available in PATH.
• Network access to https://slack.com/api.
• Access to the curated OpenAPI schema URL:
  • https://raw.githubusercontent.com/holon-run/uxc/main/skills/slack-openapi-skill/references/slack-web.openapi.json
• A Slack bot token and, for selected thread/history reads, an optional user token.

Scope

This skill covers a Messaging Core surface:

• auth validation
• channel lookup and inspection
• conversation history reads
• thread replies reads
• posting messages, including replies via thread_ts
• adding reactions

This skill does not cover:

• Slack OAuth app installation flow
• file upload flows
• users.*, admin.*, or usergroups.* method families

Subscribe / Socket Mode Status

Slack inbound events can be delivered through Socket Mode. uxc now has a built-in Slack Socket Mode transport, but this skill still treats it as a limited event-ingest path rather than a fully packaged workflow surface.

Current uxc subscribe status:

• Slack Web API request/response calls are supported by this skill
• a live Socket Mode smoke test succeeded with the built-in transport:
  • uxc subscribe start https://slack.com/api --transport slack-socket-mode --auth slack-app --sink file:...
  • the runtime opened a fresh temporary WebSocket URL automatically
  • the initial Slack hello frame was received
• a real inbound message event was validated end-to-end:
  • while the Socket Mode job was running, a live Slack message event was delivered as an events_api envelope
  • the sink recorded the message payload and ack_sent=true

What the current built-in transport already handles:

• app-level xapp-... auth via --auth
• automatic apps.connections.open before each connect attempt
• raw Socket Mode frame capture
• automatic ack for envelopes that carry envelope_id

What is still not packaged:

• event-shape guidance per subscribed Slack event family
• higher-level workflow packaging for common Slack event intake flows

Slack Socket Mode is now a validated IM subscribe provider at the transport/runtime level.

Authentication

Slack Web API uses Authorization: Bearer <token>.

Token types used in practice:

• xoxb-...: Bot User OAuth Token. This is the recommended default for this skill.
• xoxp-...: User OAuth Token. Use this only when you explicitly want user-token semantics.
• xapp-...: App-level token. Use this for Socket Mode subscribe, not for normal Web API methods.

To create an app-level xapp-... token for Socket Mode:

1. Open the target Slack app at https://api.slack.com/apps
2. Go to Basic Information
3. Find App-Level Tokens
4. Generate a token with the connections:write scope
5. Enable Socket Mode in the app configuration before relying on subscribe-based event intake

Option 1: Bot Token (Recommended Default)

Use the Slack Bot User OAuth Token (xoxb-...) for the default binding and for most messaging operations:

uxc auth credential set slack-bot \
  --auth-type bearer \
  --secret-env SLACK_BOT_TOKEN

uxc auth binding add \
  --id slack-bot \
  --host slack.com \
  --path-prefix /api \
  --scheme https \
  --credential slack-bot \
  --priority 100

Option 2: User Token (Explicit Override For Selected Reads)

Use a separate Slack User OAuth Token (xoxp-...) when the method requires user-token semantics, especially thread/history access outside bot-accessible conversations:

uxc auth credential set slack-user \
  --auth-type bearer \
  --secret-env SLACK_USER_TOKEN

Do not bind slack-user by default to the same host/path. Invoke it explicitly when needed:

uxc auth binding match https://slack.com/api
slack-openapi-cli --auth slack-user get:/conversations.replies channel=C1234567890 ts=1717171717.000100

If you intentionally want writes to appear as the installing user rather than the bot, you can also invoke write methods with --auth slack-user, but treat that as an explicit override rather than the default path.