Guide active free users toward their first paid moment

Guide active free users toward their first paid moment

Set up the tools below, then run the steps in order for the user.

Inputs

Ask the user for these before you start.

• activation_event: the event that marks real usage, e.g. campaign_sent
• trial_plan: the plan to offer, e.g. Pro, 14-day trial

Set up

Run a SQL query (PostHog, tool:posthog/run-sql-query)

Use the first option your agent supports.

MCP (official, remote)

Add this server to your agent's MCP settings, then sign in when asked.

{ "mcpServers": { "posthog": { "url": "https://mcp.posthog.com/mcp" } } }

Call the MCP tool execute-sql.

CLI (official)

Install the command, then confirm it runs.

npm install -g @posthog/cli@latest
posthog-cli --version

Run posthog-cli api call execute-sql.

Set $POSTHOG_CLI_API_KEY in your environment first (get a key: https://app.posthog.com/settings/user-api-keys?preset=mcp_server).

Stripe (tool:stripe/list-customers, tool:stripe/list-subscriptions)

Use the first option your agent supports.

MCP (official, remote)

Add this server to your agent's MCP settings, then sign in when asked.

{ "mcpServers": { "stripe": { "url": "https://mcp.stripe.com" } } }

• List customers: call the MCP tool stripe_api_read
• List subscriptions: call the MCP tool stripe_api_read

CLI (official)

Install the command, then confirm it runs.

npm install -g @stripe/cli
stripe --version

• List customers: run stripe customers list
• List subscriptions: run stripe subscriptions list

Brew (tool:brew/generate-email, tool:brew/send-email)

Use the first option your agent supports.

MCP (official, remote)

Add this server to your agent's MCP settings, then sign in when asked.

{ "mcpServers": { "brew": { "url": "https://brew.new/api/mcp" } } }

• Generate an email: call the MCP tool create_email
• Send an email: call the MCP tool send_email

CLI (official)

Install the command, then confirm it runs.

brew install getbrew/tap/brew-cli
brew-cli --version

• Generate an email: run brew-cli emails generate
• Send an email: run brew-cli emails send

Set $BREW_API_KEY in your environment first (get a key: https://brew.new/settings/api).

Make one read-only call to each tool to confirm access.

Steps

1. Find activated free users with Run a SQL query (PostHog). List users on the free plan who fired activation_event three or more times in the last 14 days.
2. Find their customers with List customers (Stripe). Look up each user's email, as stored and lowercased, and keep every customer ID it returns.
3. Skip paying customers with List subscriptions (Stripe). Remove anyone whose customer has an active subscription.
4. Write the email with Generate an email (Brew). Draft one email explaining trial_plan around what they already did. Show it to the user.
5. Send with Send an email (Brew). After the user approves, send it to the remaining users.

Done when

• No paying customer received the email.
• The user has the count of users emailed.

Rules

• Only use the tools listed above.
• Ask the user before anything that sends messages, costs money, or changes data.
• Never print API keys.