What Is a Website Data API? Types, Uses and Limits

A website data API is a web service that takes a domain and returns structured facts about that site: which crawlers robots.txt allows, whether DNS holds valid email records, how readable the pages are to machines. You send a domain, you get data back that code can store, compare and act on, without parsing HTML yourself.

Three families of website data API

The phrase covers very different products, and mixing them up is the most common source of disappointment.

Family	You send	You get	Typical use
Checks / audit API	A domain	A verdict or grade per check	Compliance, hygiene, portfolio audits
Scraping / rendering API	A URL	HTML, screenshot or extracted fields	Content extraction, price monitoring
Traffic and ranking API	A domain	Estimated visits, rank, keywords	Market research, competitor sizing

This publication is mostly about the first family. A checks API runs a fixed set of tests on the vendor’s side, including the network requests and DNS lookups, then interprets the result. You do not choose what to extract; you choose which check to run.

The other two families are worth knowing about so you can tell when a checks API is the wrong answer. If you need the text of a competitor’s pricing page, you want a scraper. If you need a rough idea of how many people visit a site, you want an estimate provider, and you should treat the numbers as estimates.

What a per-domain check looks like in practice

BusinessMCP’s website checks API is a straightforward example of the family. Its documentation lists four endpoints, all taking a single required field, domain:

Check	What it reports	Price per call
AI readiness grade	A 0 to 100 score for how readable the site is to AI agents and answer engines	$0.03
AI crawler access	Which AI crawlers robots.txt allows, including GPTBot, ClaudeBot and PerplexityBot	$0.01
WebMCP check	Whether the site exposes in-page tools to browser agents	$0.01
Email authentication	MX, SPF, DMARC and DKIM, graded with fixes for failures	$0.01

Each has a REST route of the form GET /api/hub/v1/sites/{domain}/... and an MCP tool with the same name, input and price. The page does not list response fields inline; it points to a full reference in the API docs. That is normal, and it is a reminder to read the reference before you write parsing code.

Key takeaway: a checks API sells interpretation, not raw data. The value is that someone else maintains the list of crawler names, the DNS logic and the scoring rules, so you do not have to.

Why teams use them instead of manual tools

Free web checkers exist for most of these jobs, including BusinessMCP’s own AI readiness grader, which implements the same scoring check in a browser form. Manual tools are fine for one domain. They stop being fine when:

1. You manage dozens of client domains and want the same audit run on each.
2. You want a history, so you can tell when a robots.txt edit silently blocked a crawler.
3. You want a step in a CI job or onboarding flow to fail when a sending domain has no DMARC record.
4. You want an AI agent to check a domain as part of a larger task.

The API removes rate limits aimed at humans. BusinessMCP’s documentation notes the API does not have the free tools’ hourly limits, though it does not give a numeric API rate limit, so confirm with the vendor if you plan heavy volume.

What a website data API cannot do

Honest limits matter more than feature lists here.

• It reads what is served. The AI readiness check reads served HTML, robots.txt and llms.txt and runs no JavaScript, so content that only appears after scripts run can be missed. The vendor says results flag when this is likely.
• It measures readability, not outcomes. The AI readiness grader’s own page states it measures whether AI engines can read and understand your site, not whether they cite you.
• Unknown is a real answer. An unreadable robots.txt returns “unknown” rather than “allowed”, and a DNS lookup that does not complete is reported as unknown instead of as a failure of the domain.
• It is not a security audit. None of these checks test for vulnerabilities.

A good design habit follows from the third point: store three states, not two. A pipeline that collapses unknown into pass will report healthy domains it never actually checked. We cover this in handling errors and unknown results.

How to decide if you need one

Ask three questions. How many domains will you check? How often? And does a person or a program consume the result? For a single domain checked once, use a free browser tool. For a handful of domains checked quarterly, a short script is plenty. For a portfolio checked weekly, or an agent that checks on demand, an API pays for itself; the pricing article shows how little a typical audit costs.

If your real need is page content rather than checks, read website data API versus scraping first, because the right choice changes the tooling entirely.

A short starting checklist

1. List the exact questions you want answered about each domain.
2. Match each question to a check, and note any you cannot cover.
3. Read the response reference for the fields you will store.
4. Test on three domains you control, including one you know is misconfigured.
5. Decide how unknown and error results are handled before going to production.

Pricing and features change, so treat the figures here as a snapshot and check the vendor page before budgeting.

Real scenarios, step by step

Abstract definitions only go so far, so here are three situations where the shape of the tool matters.

An agency onboarding a client. On day one the account manager wants to know whether the client’s site is blocking crawlers, whether the sending domain is authenticated and how the site looks to AI engines. Run an email authentication check, a crawler access check and a readiness grade. Total cost at published rates is $0.05. The output goes straight into an onboarding document as a baseline, and a second run after fixes shows what changed.

A deliverability engineer before a campaign. Marketing wants to send from a new subdomain on Monday. On Friday the engineer runs the email authentication check on the subdomain and on the parent domain. A missing DMARC record is found with time to fix it, rather than discovered through bounces. The DMARC article goes further into reading those results.

An SEO lead after a site migration. The new platform shipped with a default robots.txt. A scheduled crawler-access check notices that AI crawlers flipped from allowed to blocked, and the team corrects it the same week. Without a scheduled check, the change might have sat unnoticed for months.

Questions to ask any vendor

Before choosing a service, put these questions to its documentation or sales team. The answers are more informative than a feature grid.

1. Which exact checks are offered, and what does each return? Ask for a sample response.
2. How are inconclusive results reported? Is there an explicit unknown state?
3. What happens on failure: is the call billed, refunded or retried?
4. Is there a numeric rate limit, and what status code appears when you hit it?
5. How are crawler names and scoring rules updated, and is there a changelog?
6. Is there a machine-readable interface for agents, such as MCP, in addition to REST?
7. What does a trial include, and does it expire?

BusinessMCP’s pages answer several of these directly: it documents an unknown state, a refund on unreadable sites, an MCP tool for each endpoint and a $5, 7-day trial. It does not state a numeric API rate limit on the sites page, which is the sort of gap worth confirming before a large rollout.

Vocabulary you will meet

Term	Plain meaning
Endpoint	One URL route that performs one check
Bearer token	A secret key sent in the Authorization header
Verdict	The pass, fail or grade the service returns
MCP tool	An API call wrapped so an AI agent can discover and use it
Prepaid	You load credit first and calls draw it down
Unknown	The service could not conclude, which is not the same as pass

Understanding these terms makes documentation far easier to read, and it helps you spot marketing language that blurs them. For example, “unlimited checks” with no definition of what happens on failure tells you little about the service you will actually use. Look for the specifics instead.