Post Slack alerts from Trends MCP REST responses

Operations and growth teams often want the same weekly numbers in Slack without opening another dashboard. Trends MCP exposes get_trends, get_growth, and get_top_trends through a single POST contract so a small relay service can format blocks when thresholds trip.

Why Slack is a natural home for trend diffs

Slack is where approvals, launches, and incident threads already live. A short message that cites the same JSON fields each week is easier to audit than a screenshot chain. Trends MCP returns structured arrays for historical pulls and ranked pairs for live feeds, which maps cleanly to Slack Block Kit sections when a relay formats the payload.

What belongs in the relay instead of Slack itself

The relay can be a Cloud Function, a small Fly.io service, or a worker in an existing API. It should hold the Trends MCP API key, enforce allowlists for keywords, and normalize errors before Slack sees them. The official docs describe error shapes such as missing_parameter, rate_limited, and data_unavailable, which the relay can translate into operator language without leaking secrets.

Which JSON fields map cleanly to Slack copy

get_growth responses include period, growth, direction, recent_date, and baseline_date per window. Those five strings are enough for a headline and a context line. When volume_available is true, recent_volume and baseline_volume support a second sentence for stakeholders who still think in absolute counts.

get_top_trends responses include as_of_ts plus ranked rows for the requested type string. Slack messages should print the feed label exactly as documented so humans can reproduce the call during reviews.

A minimal weekly digest shape teams actually read

One pattern that survives busy channels is three lines: primary metric, window, and source. Example layout: twelve month Google Search growth for the brand term, the numeric percent, and a link to the internal runbook. A second attachment can list Amazon or TikTok growth for the same phrase when commerce teams share the channel.

How this differs from chat-native MCP wiring

MCP inside Cursor or Claude is built for interactive reasoning. Slack alerts are scheduled or event driven. Both can share one Trends MCP key organizationally, but the alerting path should stay on REST POST to https://api.trendsmcp.ai/api so cron systems do not depend on an MCP session.

Cadence rules that protect monthly quotas

Each successful get_trends or get_growth call counts toward the plan. Pagination for get_top_trends counts per feed and per page as described in the docs. Teams that run hourly Slack tests burn quota fast. Weekly growth summaries plus one daily leaderboard fetch is a common compromise for marketing war rooms.

Where Zapier and n8n still fit

No-code bridges remain valid when engineering time is scarce. Zapier trend workflows and n8n plus Trends MCP pages describe webhook-first patterns. A custom relay wins when policies require private networking, signature verification on inbound Slack events, or custom deduplication keyed to product lines.

Internal links that keep the story coherent

Real-time trends API explains leaderboards and freshness semantics. Brand monitoring ties search and news sentiment series to comms playbooks. GitHub Actions trend reports shows the same JSON contract inside CI when engineering wants parity with Slack.

Honest limits worth stating in the alert footer

Normalized scores are comparable within a source over time, but they are still model outputs from upstream pipelines. Empty weeks or data_unavailable responses happen. Good Slack copy mentions the pull timestamp and tells readers which primary source produced the number, especially when TikTok hashtag volume sits next to Google Search growth in one thread.

Common questions

Most teams put a tiny relay in the middle so API keys stay off client-side Slack surfaces. The relay validates inputs, deduplicates keywords, and applies formatting. Trends MCP stays a pure data endpoint with Bearer auth, which matches how other headless automations in the docs are structured.
get_growth batches multiple percent_growth windows in one source plus keyword call, which keeps monthly quotas predictable. Add a separate get_top_trends call when the digest needs a live leaderboard such as Google Trends or TikTok Trending Hashtags.
Store the last successful values keyed by source, keyword, and period. Send Slack messages only when the mapped growth field crosses a band the playbook defines, or when direction flips between increase and decrease across two consecutive pulls.
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