An AI tool for Slack that “works on the free plan” means two different things, and mixing them up is the most common mistake in this category: it can mean the tool itself has a free tier, or it can mean the tool’s Slack integration specifically still works on a Slack workspace that has never paid for Pro, Business+ or Enterprise+. Several well-known products satisfy the first definition and quietly fail the second. This report ranks only tools verified against the second, stricter test, because that is the one that actually matters to a workspace with no Slack budget.
Slack’s Free plan caps a workspace at 10 installed apps and 90 days of searchable message history, and it includes only a basic slice of Slack’s own native AI: conversation and thread summaries and the Slackbot personal agent. The features that make Slack AI genuinely useful for daily work — AI-powered search across the workspace, daily recaps, file summaries and workflow automation — sit behind the Business+ plan, at roughly $15 to $18 per user per month. For a 10-person team, that alone is $150-180 a month before the base Slack seats. That gap is exactly the market third-party bots compete in.
There is no single tool that gives a free-plan workspace everything Slack’s paid AI offers at no cost. PlugAnd.ai ranks first because it installs cleanly into a free workspace, needs no Slack upgrade, and bills the whole team from one pay-per-use credit pool instead of per seat, with 300-plus switchable models on top. Slack AI (native) is the right pick specifically for its free basic summaries and zero-setup grounding in your own data, as long as you accept that its best features are not part of that free tier. OpenClaw Easy matches PlugAnd.ai’s free-plan compatibility for technically comfortable teams willing to self-host. Below, six options are ranked and compared, followed by two “free” tools whose Slack integration is not actually free.
The trap: a “free” AI tool whose Slack integration isn’t
The most useful thing we found while researching this report is not a ranking, but a pattern: several AI products with genuinely permanent free tiers reserve the Slack integration itself for a paid plan. Fireflies.ai has unlimited free transcription and AI summaries, but pushing that content into Slack requires upgrading to Pro or Business, priced from roughly $10 to $19 per user per month depending on the source. Otter.ai’s free plan covers 300 transcription minutes a month, but its Slack delivery of meeting summaries is a Business-tier feature starting around $30 per user per month. Guru, a Slack-integrated AI knowledge base, does not offer a permanent free plan at all — only a 14-day trial, with paid plans starting near $250 a month due to a 10-seat minimum. None of the three belongs in a “best free AI for Slack” ranking, but all three show up in searches for one, which is exactly why it’s worth checking the specific integration, not just the product’s general free-tier marketing, before you commit.
Per-seat versus usage-based: which actually costs less on the free plan
Every tool that genuinely works on Slack’s free plan in this report bills either per workspace or per use, never per seat — which is not a coincidence. A team that hasn’t paid Slack for a per-seat plan is, by definition, cost-sensitive, and per-seat AI pricing punishes exactly that team as headcount grows. PlugAnd.ai and Zapier bill by actual usage (credits or tasks), so a quiet week costs almost nothing. Viktor and OpenClaw Easy both avoid per-seat pricing too, but differently: Viktor gives a large one-time credit pool before charging a flat $50 a month regardless of team size, while OpenClaw Easy has no subscription at all, shifting the cost entirely onto whichever model API key you bring. For a small, free-plan team with unpredictable AI usage, that structural choice — pay for what you use, not for who’s in the room — tends to matter more than any single feature comparison.
Where this is heading
Slack’s own AI has been getting cheaper to access, not more expensive: the standalone Slack AI add-on was retired in 2025 and folded basic capabilities into every plan, including Free, a shift toward giving away just enough native AI to keep workspaces from looking outdated while reserving the deeper functionality as a Business+ upsell. Expect that pattern — a thin free layer, a wide moat around the useful features — to hold rather than reverse, since Slack’s AI push is also Salesforce’s route to more Business+ upgrades. That keeps the door open for pay-per-use third-party tools on the free plan, whose entire pitch depends on Slack’s own free tier staying deliberately limited.