Public API Overview

The Simmer Public API lets you connect backend systems, reporting tools, and internal workflows to your Simmer project. Use it when you want to send conversion events from your server, pull attributed marketing metrics, or inspect recent visitor activity programmatically.

Base URL

All Public API endpoints are served from:

https://app.letsimmer.com

Endpoint paths are versioned under /api/v1. For example:

POST https://app.letsimmer.com/api/v1/conversions
GET https://app.letsimmer.com/api/v1/overview

Create API keys

Create and revoke Public API keys from your project's API page in the dashboard. Keys are project-scoped and are shown in full only once when created.

The API page also shows connected MCP clients. MCP connections are project-scoped and read-only.

The API page also includes the legacy server-side conversion key for older /api/conversion integrations. New integrations should use /api/v1/conversions with a Public API key that has conversions:write.

Versioning

The v1 path segment is the API version. Backward-compatible additions may appear within the same version, such as new optional response fields or new endpoints. Breaking changes will be introduced under a new versioned path.

Date filtering

Endpoints that accept from, to, and timezone use calendar dates:

Date ranges can span up to 180 days. Requests with a larger range or an unknown timezone return invalid_date_range.

Reporting endpoints use date_basis: conversion_date, so a conversion on the from date or to date is included when it falls within those calendar-day boundaries in the requested timezone.

Activity endpoints use date_basis: activity_date, so visitor activity is included when the activity occurred within the requested calendar-day boundaries.

Reporting vs. activity resources

Reporting resources answer questions about conversion performance:

• Overview metrics summarize attributed conversions and attributed revenue.
• Channel metrics show how channels contributed across the selected date range.
• Conversion journeys explain the touchpoints behind attributed conversions.

Insights resources answer questions about website traffic and conversion rate:

• GET /api/v1/insights returns aggregate visitors, sessions, pageviews, visit-to-lead CVR, and visit-to-sale CVR for the selected date range.
• GET /api/v1/insights/channels returns sessions, pageviews, visit-to-lead CVR, and visit-to-sale CVR broken down per channel, with pagination. Visitor counts are only available at the aggregate level.

Activity resources help you explore recent visitor behavior that has not yet converted:

• Unconverted visitors list anonymous visitors with browsing activity.
• Visitor detail shows the activity timeline known for one anonymous visitor.

Use reporting endpoints for dashboards and recurring analysis. Use Insights endpoints for traffic volume and conversion-rate analysis. Use activity endpoints for investigation, sales assist workflows, and operational follow-up.

Conversion journey filters support lead, sales_qualified_lead, deal_closed_won, and order as conversion_type values. Unknown values are rejected so typos do not look like empty reports.

When filtering by conversion_type=lead, results include Untracked leads — form-source HubSpot contacts where no browsing history could be linked. These rows have credited_channel: null, touchpoint_count: 0, and empty sessions and touchpoints arrays. Use credited_channel to distinguish them: a non-null value means the lead has channel attribution; a null value means it is untracked.

Migration note: CVR and visitor fields

conversion_rate and visitors were removed from the /api/v1/channels and /api/v1/overview responses in v1. These metrics now live in the Insights resources above. Requests that depend on those fields should be updated to read from /api/v1/insights or /api/v1/insights/channels.

API Reference

See the API Reference for endpoint parameters, request bodies, response schemas, and required scopes.

See MCP to connect Claude or another MCP client to read project data.