| name | post-to-slack |
| description | Post a message to a Slack channel, resolving channel/user names to IDs and adding an optional @mention or thread reply. Use when the user wants to post, share, or notify something in Slack, or when another skill needs to deliver its output to a Slack channel. |
| disable-model-invocation | true |
Post to Slack
Resolves a channel name (or a user name for a mention) to its Slack ID
before posting — the Slack MCP connector's send/search tools need IDs, not
display names, and IDs are not stable across workspaces.
Steps
- Determine the message body and the target channel. If the caller (a
direct user request, or another skill such as
report-pbl-progress)
already gives an explicit channel ID (C...) and/or an already-resolved
mention (<@U...>), skip straight to step 4 — don't re-resolve what's
already unambiguous.
- If the channel is given by name rather than ID, resolve it with the Slack
MCP connector's
slack_search_channels tool and take the matching
channel's ID. If more than one channel plausibly matches, ask the user
rather than guessing.
- If a mention is wanted and given by name rather than user ID, resolve it
with
slack_search_users and format it as <@USERID> inline in the
message text — Slack does not render @name as a mention, only the raw
<@ID> form works.
- Post with
slack_send_message (thread_ts for a thread reply,
reply_broadcast to also surface a thread reply in the channel). Return
the message's permalink to the caller.
Reference
Failure modes
- Channel not found:
slack_search_channels found no match — confirm
the exact channel name with the user; don't guess a close match.
- User not found: same for
slack_search_users when resolving a
mention.
- Message too long: 5000 characters per text element — split into a
thread reply rather than truncating silently.
- Can't post to Slack Connect (externally shared) channels:
slack_send_message fails outright for these; tell the user rather than
retrying.
- Slack Canvas unavailable:
slack_create_canvas returns
not_supported_free_team on free-tier workspaces. This skill never uses
Canvas for that reason — if a caller wants a richer document than a
single message, that's out of this skill's scope.
Reusable from other skills
This skill is intentionally generic — it has no PBL/monday-specific logic.
Any skill that produces a summary a human should see in Slack (e.g.
report-pbl-progress) should hand this skill the message text and target
channel rather than calling the Slack MCP tools directly itself. This also
keeps unattended/scheduled callers working: a caller that already knows its
channel and mention can drive this skill's steps straight through without
any ambiguity to resolve.
