Follow Up Boss API Integration Guide

What is the Follow Up Boss API and what can you build with it?

Follow Up Boss (owned by Zillow Group) exposes a REST API that lets developers read and write CRM data programmatically. The API covers the full breadth of FUB's data model:

• People (contacts) — create, update, search, and retrieve lead records with their full field set
• Events — log activity (calls, emails, form submissions, SMS) against contact timelines
• Notes — read and write notes on contacts, deals, and calls
• Custom fields — write to any custom field configured on the account, including AI-derived fields
• Tasks — create and complete follow-up tasks
• Deals — manage transaction pipeline stages
• Webhooks — receive real-time push notifications when contacts are created, updated, or take action

For real estate use cases, the most common integration patterns are: lead ingestion from external sources, webhook-driven score updates, bulk contact enrichment, and custom reporting pipelines.

How does Follow Up Boss API authentication work?

The Follow Up Boss API uses HTTP Basic Authentication. Your API key is the username; the password field can be left blank or set to any non-empty value — it is not validated.

Every request must include the Authorization header with a Base64-encoded value of api_key::

Authorization: Basic base64(YOUR_API_KEY:)

Retrieve your API key from the Follow Up Boss admin dashboard under Admin → API. Each key is scoped to the account; there is no per-user key scope in the v1 API. For current authentication details and any changes, see the official documentation at followupboss.com/developers.

What are the key Follow Up Boss API endpoints?

The base URL for all v1 API requests is https://api.followupboss.com/v1/. Key endpoints by resource:

How do Follow Up Boss webhooks work?

Webhooks are the most important part of any real-time FUB integration. Instead of polling the API for new data, you register an HTTPS endpoint; FUB sends a POST request to that endpoint whenever the subscribed event fires.

Common webhook event types include:

• personCreated — a new contact was added to the account
• personUpdated — a contact's fields were modified
• eventCreated — an activity event (call, email, form fill) was logged
• noteCreated — a note was added to a contact

To register a webhook via the API:

1. POST to https://api.followupboss.com/v1/webhooks with a JSON body specifying your callback URL and the event types you want to receive.
2. Confirm that your endpoint returns a 200 OK response within the timeout window; FUB will retry failed deliveries.
3. Process the incoming POST payload in your handler — each payload includes the event type, the affected entity ID, and changed field data.

Follow Up Ace uses exactly this mechanism to update Ace Score, Ace Tier, and the other behavioral fields in real time. Every time a contact takes an action tracked in FUB, the webhook fires, Ace processes the event, and the custom fields update on the contact card within seconds.

How do you connect Airtable, Mailchimp, and email parsers to Follow Up Boss?

Each connection method trades setup effort for control:

Tool-by-tool, the practical path is:

• Airtable → Follow Up Boss: use Zapier or Make. A "new/updated record" trigger in Airtable maps to FUB's "create or update person." For two-way sync (FUB changes back to Airtable), add a second automation driven by a FUB personUpdated webhook.
• Mailchimp / Constant Contact → Follow Up Boss: connect through Zapier (or a native connector if one is listed). Sync subscribers as FUB contacts, and log opens and clicks as FUB /events so email engagement shows on the contact timeline.
• Email parser → Follow Up Boss: for portal leads, the simplest route is the FUB lead-parsing email address — no parser to configure. For non-standard sources, a parsing service (or your own code) can extract the fields and POST them to /people.
• Webhooks for any tool: when you need FUB changes to push outward to another system in real time, subscribe to personCreated/personUpdated/eventCreated as shown above and forward the payload to the destination.

Where does an AI assistant like Follow Up Ace fit? Ace is not a data-sync connector — it does not replace Zapier or a native integration. It runs inside Follow Up Boss on the data those integrations land, reading and writing through the same API and webhooks to score, segment, and draft follow-up. Browse pre-built connectors on the Follow Up Ace integrations page, and use the methods above for anything that needs to move records between FUB and another app.

What are the Follow Up Boss API rate limits?

Follow Up Boss enforces rate limits on API requests to protect platform stability. Exact limits and enforcement rules are defined by Zillow Group and may change; always check the current policy at followupboss.com/developers. General guidance for integrations:

• Implement exponential backoff when you receive a 429 Too Many Requests response
• Batch writes where possible — updating multiple fields on a contact in a single PUT is more efficient than multiple requests
• Use webhooks for real-time data rather than polling; polling at high frequency is the most common cause of hitting rate limits
• Cache read data (especially list endpoints like /customFields and /users) with a reasonable TTL rather than fetching on every operation

How do you write custom field values via the FUB API?

Custom fields in Follow Up Boss are written as part of the contact (person) update payload. The field name must match the name value configured in the account's custom field settings — for example, customAceScore, customAceTier.

A minimal PUT request to update Ace Score on a contact looks like:

PUT https://api.followupboss.com/v1/people/{id}
Content-Type: application/json

{
  "customAceScore": 78,
  "customAceTier": "Hot"
}

Dropdown fields (like Ace Tier) accept the string value matching one of the configured choices. Number fields accept an integer or float. Text fields accept a string. Confirm the field type and choices in /customFields before writing to avoid type errors.

How does AI extend the Follow Up Boss API surface?

One of the most practical extensions is natural-language CRM control via the Model Context Protocol (MCP). Follow Up Ace exposes 215 tools over MCP — covering contacts, events, notes, tasks, deals, tags, action plans, and more — and those tools are accessible to AI assistants like Claude via a single connection URL.

Connecting Claude Desktop: add https://followupace.com/mcp as a remote MCP server. Connecting ChatGPT or other SSE-based clients: use https://followupace.com/api/mcp/sse/. Once connected, you can type natural language requests — "find all contacts tagged Zillow who haven't been called in 30 days" — and the AI executes the underlying API calls through Follow Up Ace.

This removes the need to write API queries manually for routine database tasks. See the Agentic overview for the full scope of what's available. The MCP connection requires a Pro plan.

What are the most common Follow Up Boss API integration mistakes?

• Hardcoding contact IDs — always look up contacts by email or phone before writing; IDs can change between environments
• Ignoring webhook retry behavior — if your handler doesn't return 200 quickly, FUB retries. If your handler isn't idempotent, this creates duplicate records or double-logged events. Design handlers to be safe to re-run.
• Skipping custom field setup — custom fields must be configured in the FUB admin before you can write to them via the API. A PUT to an unconfigured field name will silently fail or be ignored.
• Over-polling — checking /people every 30 seconds for changes is unnecessary and rate-limit-unfriendly. Use webhooks for change notifications.
• Not validating field names — field names are case-sensitive and must match the configured name value exactly, including camelCase capitalization.

What if I want AI to manage FUB integrations for me instead of coding?

That's exactly the use case the MCP interface is designed for. Instead of writing integration code, an agent connected to Follow Up Ace via MCP can execute API operations through natural language. Creating a contact, logging a call, adding a tag, running a search — all available as AI-executable tools.

For teams that want the power of the FUB API without the development overhead, this is the practical alternative. The 215-tool MCP surface covers most workflows that would otherwise require custom integration code. Start at the Guides section or try How to Use API Docs for Follow Up Boss Integration for the developer path.

Related reading: Checklist for Setting Up API Triggers · FUB API Real-Time Integration Explained · Agentic overview