Can ChatGPT use the Zillow API?

Yes, through custom GPTs. ChatGPT's Actions feature accepts any OpenAPI 3.1 spec, and Zillapi publishes one at zillapi.com/openapi.json. Import the spec, paste a bearer token, and the GPT can call lookup_property_by_address, get_zestimate, search_listings, and the rest of the API surface.

Do I need ChatGPT Plus or Team to build a custom GPT?

Yes. Custom GPTs and Actions are available on ChatGPT Plus, Team, Enterprise, and Edu plans. Free ChatGPT can use published GPTs but cannot create them. The Zillapi REST API itself is free for the first 100 calls regardless of which ChatGPT plan you're on.

Can I publish my custom Zillow GPT to the GPT Store?

Yes. The Zillapi terms allow building public GPTs on top of the API. Each GPT user has to provide their own Zillapi key — OpenAI does not let the GPT publisher share a single key across all users. Have your users sign up at zillapi.com/signup and paste their key during the OAuth-style first-use flow.

How is using ChatGPT Actions different from MCP for Zillow?

ChatGPT Actions are GPT-specific and consume an OpenAPI spec. MCP is portable across Claude, Cursor, ChatGPT's Agents SDK, and other clients. If you only need the integration inside one custom GPT, Actions are simpler. If you want the same integration to work in Claude, Cursor, and the Agents SDK without rewiring, use MCP at api.zillapi.com/mcp.

What about the OpenAI Agents SDK and Zillow?

The OpenAI Agents SDK supports MCP servers directly. Point its MCPServerSse or MCPServerStreamableHTTP at https://api.zillapi.com/mcp with your bearer token and the agent gets the same four tools as Claude and Cursor. The Actions-via-OpenAPI path described in this article is for custom GPTs inside ChatGPT, not for SDK-built agents.

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Use Zillow data in ChatGPT custom GPTs

Wire Zillapi into a ChatGPT custom GPT as an Action. OpenAPI import, bearer auth, and the prompts that make the GPT route property questions.

By Zillapi May 12, 2026

Give a ChatGPT custom GPT access to live Zillow data in five minutes. Get a free Zillapi key — 100 credits, no card required — point the GPT’s Actions tab at zillapi.com/openapi.json, paste the bearer token, and the GPT pulls Zestimates, listings, schools, and the full 300-field property record on its own.

This guide is the OpenAPI import flow, the auth setup, the system prompt that makes routing reliable, and a few example prompts to confirm it works.

Step 1: Get a Zillapi API key

Step 2: Open the GPT editor

In ChatGPT, click Explore GPTs in the left sidebar, then Create (or open an existing GPT and click the pencil icon to edit). Open the Configure tab.

Scroll past the basic fields (name, description, instructions, conversation starters) to Actions at the bottom.

Step 3: Import the Zillapi OpenAPI spec

Click Create new action, then Import from URL in the schema box, and paste:

https://zillapi.com/openapi.json

ChatGPT fetches the OpenAPI 3.1 document and lists every operation — getPropertyByAddress, getPropertyByUrl, getPropertyByZpid, getPropertyZestimate, listingsBbox, and the rest. You don’t need to edit anything; the spec is valid as-is.

Step 4: Add bearer authentication

Under Authentication click API Key. Set:

Auth Type: Bearer
API Key: zk_YOUR_KEY

Save. ChatGPT injects the Authorization: Bearer zk_... header on every Action call.

Step 5: Tune the instructions for clean routing

In the GPT’s main Instructions field, add:

You have access to the Zillapi real estate API. Use it whenever the user
mentions a U.S. property address, a Zillow URL, a Zestimate, a property
search, or comparable sales.

- For one specific property: getPropertyByAddress or getPropertyByUrl.
- For Zestimate only (cheaper): getPropertyZestimate.
- For a list of properties: listingsBbox with the location or bbox.
- Never ask the user for an API key — the key is configured.

If a tool call returns an error object with code 429, tell the user the
account is rate-limited and to try again in a minute.

Without that paragraph, the GPT sometimes asks the user to confirm before calling the tool. With it, the GPT routes property questions to the right Action on the first turn.

Step 6: Test in the preview pane

Type prompts like:

“What’s the Zestimate on 17 Zelma Dr, Greenville SC?”
“Find homes for sale in Austin TX under $500k.”
“Pull the full record from this Zillow URL.”

The first time the GPT calls an Action, ChatGPT shows an “Always allow” prompt. Approve it.

Troubleshooting

The Action calls return 401 Unauthorized. The bearer key is wrong or has been revoked. Open the Authentication settings, paste the key again (no Bearer prefix — ChatGPT adds that for you), and save.

The GPT keeps asking the user for an API key. You typed Bearer zk_... into the API Key field. Remove the Bearer prefix — ChatGPT inserts it automatically. The field should contain only zk_....

The GPT picks the wrong operation. Either the user prompt is ambiguous, or the GPT instructions are missing the routing rules. Paste the instructions block from Step 5 verbatim.

Calls return 429 Too Many Requests. Rate limit. Free is 20/min, Monthly is 200/min. ChatGPT can fire multiple Actions in parallel during a long answer, so even modest usage hits the Free ceiling fast. Upgrade if you ship the GPT publicly.

The published GPT fails for other users. Each ChatGPT user has to supply their own Zillapi key — OpenAI does not let GPT publishers share one key across all users. Add a conversation starter like “Set your Zillapi API key” and instruct the user how to do it from the Actions settings.

What you can ship with this

A few things you can do with a Zillow-equipped custom GPT in under an hour:

A neighborhood-research GPT that takes a city and price range and produces a one-page market summary.
A comp-pulling GPT that takes a subject property and produces a list of recently sold comparables.
An investor-screening GPT that takes an address and outputs a quick yield analysis based on the Zestimate, rent Zestimate, and tax history.
A buyer-agent GPT that searches active listings against the user’s saved preferences and returns the top five.

The same Zillapi key works in Claude Desktop, Claude Code, Cursor, the OpenAI Agents SDK (via the MCP server), and the open-source skills repo. One key, every agent.

Don’t have a key yet? Sign up free at zillapi.com/signup — 100 credits, no card required. Paid plans start at $5/month if you outgrow it.

Frequently asked questions

Can ChatGPT use the Zillow API?: Yes, through custom GPTs. ChatGPT's Actions feature accepts any OpenAPI 3.1 spec, and Zillapi publishes one at zillapi.com/openapi.json. Import the spec, paste a bearer token, and the GPT can call lookup_property_by_address, get_zestimate, search_listings, and the rest of the API surface.
Do I need ChatGPT Plus or Team to build a custom GPT?: Yes. Custom GPTs and Actions are available on ChatGPT Plus, Team, Enterprise, and Edu plans. Free ChatGPT can use published GPTs but cannot create them. The Zillapi REST API itself is free for the first 100 calls regardless of which ChatGPT plan you're on.
Can I publish my custom Zillow GPT to the GPT Store?: Yes. The Zillapi terms allow building public GPTs on top of the API. Each GPT user has to provide their own Zillapi key — OpenAI does not let the GPT publisher share a single key across all users. Have your users sign up at zillapi.com/signup and paste their key during the OAuth-style first-use flow.
How is using ChatGPT Actions different from MCP for Zillow?: ChatGPT Actions are GPT-specific and consume an OpenAPI spec. MCP is portable across Claude, Cursor, ChatGPT's Agents SDK, and other clients. If you only need the integration inside one custom GPT, Actions are simpler. If you want the same integration to work in Claude, Cursor, and the Agents SDK without rewiring, use MCP at api.zillapi.com/mcp.
What about the OpenAI Agents SDK and Zillow?: The OpenAI Agents SDK supports MCP servers directly. Point its MCPServerSse or MCPServerStreamableHTTP at https://api.zillapi.com/mcp with your bearer token and the agent gets the same four tools as Claude and Cursor. The Actions-via-OpenAPI path described in this article is for custom GPTs inside ChatGPT, not for SDK-built agents.