OnTheMarket

OnTheMarket is the third-largest residential property portal in the United Kingdom, operating onthemarket.com. It was founded in 2013 by Agents' Mutual Limited as an agent-owned challenger to Rightmove and Zoopla, listed on AIM as OnTheMarket plc, and was acquired outright by CoStar Group in December 2023 for approximately GBP 99 million. In a market with no MLS and no cooperative listing standard, OnTheMarket sits at the demand end of the value chain: consumers search the portal, and listings arrive from member estate agents' CRM systems rather than from a shared data pool. Its API posture is honest and narrow. There is no public developer portal — developer., developers., api. and docs.onthemarket.com do not resolve, and /developers, /api, /docs, /openapi.json, /swagger.json and /api-docs all return 404 on the main site. What does exist is a member-only integration surface: the OnTheMarket Real Time Datafeed (RTDF), a Rightmove-RTDF-compatible feed API served from the live, OnTheMarket-operated host realtime-api.onthemarket.com, used by agency CRM vendors to push listings and pull branch enquiries on behalf of member agents. No machine-readable contract for it is published anywhere; OnTheMarket's developer guide is distributed under agreement, and every path on the host returns 404 to an anonymous caller. There is no RESO Web API or Data Dictionary certification, no OData $metadata document and no Universal Property Identifier anywhere in the stack — RESO is a North American construct and the UK has never adopted it, so "certified but unreachable" does not apply here; there is no certification layer in this market at all. OnTheMarket publishes no open data. The genuinely open UK property layer belongs to the public sector — HM Land Registry Price Paid Data and Ordnance Survey — and none of it comes from the portals. OnTheMarket's own Terms of Use go further than most and expressly forbid automated access to any page other than the home page.

OnTheMarket is listed with 1 API on the APIs.io network. Tagged areas include Real Estate, United Kingdom, Property Listings, Property Portal, and PropTech.

OnTheMarket’s developer surface includes engineering blog, support, signup flow, and 21 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

16.7/100 emerging ▬ flat Agent 0/100 human only Front door AI 1/6 silent Heartbeat 100/100 alive saas Full breakdown ↓
scored 2026-11-13 · rubric v0.28.0 · Show this score on your site →

1 API

Real Estate United Kingdom Property Listings Property Portal PropTech Rentals Estate Agents Data FeedNew HomesCommercial Real Estate

Kin Score

Kin Score How this is scored →
scored 2026-11-13 · rubric v0.28.0

Composite quality — 16.7/100 · emerging

Contract Quality 0.0 / 21

Developer Ergonomics 1.2 / 17

Access Clarity 6.5 / 17

Operational Transparency 0.5 / 11

Contract Governance 0.0 / 10

Discoverability 6.2 / 9

Regulatory Posture 1.9 / 15

Agent readiness — 0/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

Machine-Readable Contract +18 pts — api_specs includes an OpenAPI document Ask about this →
MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship Ask about this →
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author Ask about this →
Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey) Ask about this →
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented) Ask about this →
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes Ask about this →

13 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 0.0 — up to +25.0 composite points Ask about this →
Developer Ergonomics scores 7.1 — up to +18.6 composite points Ask about this →
Operational Transparency scores 4.8 — up to +12.4 composite points Ask about this →

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

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Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/onthemarket/apis.yml: open an issue on github.com/api-evangelist/onthemarket to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 1

Individual APIs this provider publishes, each with its own machine-readable definition.

OnTheMarket Real Time Datafeed (RTDF) API

OnTheMarket's member-only feed API for estate-agency CRM software. It is modelled on the Rightmove Real Time Datafeed (RTDF/ADF) specification, with OnTheMarket-specific differe...

Terms of Service 1

What its API terms permit and prohibit, quoted from its own page.

OnTheMarket

11 quoted statements, read from OnTheMarket's own page on 2026-11-10.

TERMS

Eligibility 1

Who may sign up and where, quoted from its own terms.

OnTheMarket

2 quoted statements, read from OnTheMarket's own page on 2026-11-10.

ELIGIBILITY

AI Preferences 1

Its stance on AI training, inference and agents, quoted from its own pages.

OnTheMarket

1 quoted statement, read from OnTheMarket's own page on 2026-11-10.

AI PREFS

Data License 1

How its data and outputs may be reused, quoted from its own terms.

OnTheMarket

1 quoted statement, read from OnTheMarket's own page on 2026-11-10.

LICENSE

Security Posture 1

Authentication, domain security, vulnerability disclosure, and trust-center signals.

OnTheMarket Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Resources

Get Started 2

Portal, sign-up, and the first successful call

SignUp

SignUp

Login

Documentation 1

Reference material describing how the API behaves

AIPreferences

AIPreferences

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

LLMsTxt

LLMsTxt

LLMsTxt

LLMsTxt

Design & Contract 2

Pagination, idempotency, versioning, errors, and events

Conformance

Conformance

Lifecycle

Lifecycle

Build 2

SDKs, sample code, and the tooling you integrate with

Packages

Packages

GitHubOrganization

GitHubOrganization

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Operate 2

Status, limits, changes, and where to get help

HelpCenter

HelpCenter

Support

Support

Commercial 4

Pricing, plans, and the legal terms of use

TermsOfService

PrivacyPolicy

UsageTerms

DataLicense

Company 6

The organization behind the API

Website

About

Blog

BlogRSS

Partners

LinkedIn

Other 2

Properties that don't map to a standard resource type

ParentCompany

ParentCompany

Eligibility

Eligibility

Source (apis.yml)

aid: onthemarket
url: https://raw.githubusercontent.com/api-evangelist/onthemarket/refs/heads/main/apis.yml
name: OnTheMarket
kind: company
description: 'OnTheMarket is the third-largest residential property portal in the United Kingdom, operating onthemarket.com.
  It was founded in 2013 by Agents'' Mutual Limited as an agent-owned challenger to Rightmove and Zoopla, listed on AIM as
  OnTheMarket plc, and was acquired outright by CoStar Group in December 2023 for approximately GBP 99 million. In a market
  with no MLS and no cooperative listing standard, OnTheMarket sits at the demand end of the value chain: consumers search
  the portal, and listings arrive from member estate agents'' CRM systems rather than from a shared data pool. Its API posture
  is honest and narrow. There is no public developer portal — developer., developers., api. and docs.onthemarket.com do not
  resolve, and /developers, /api, /docs, /openapi.json, /swagger.json and /api-docs all return 404 on the main site. What
  does exist is a member-only integration surface: the OnTheMarket Real Time Datafeed (RTDF), a Rightmove-RTDF-compatible
  feed API served from the live, OnTheMarket-operated host realtime-api.onthemarket.com, used by agency CRM vendors to push
  listings and pull branch enquiries on behalf of member agents. No machine-readable contract for it is published anywhere;
  OnTheMarket''s developer guide is distributed under agreement, and every path on the host returns 404 to an anonymous caller.
  There is no RESO Web API or Data Dictionary certification, no OData $metadata document and no Universal Property Identifier
  anywhere in the stack — RESO is a North American construct and the UK has never adopted it, so "certified but unreachable"
  does not apply here; there is no certification layer in this market at all. OnTheMarket publishes no open data. The genuinely
  open UK property layer belongs to the public sector — HM Land Registry Price Paid Data and Ordnance Survey — and none of
  it comes from the portals. OnTheMarket''s own Terms of Use go further than most and expressly forbid automated access to
  any page other than the home page.'
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: false
  label: Hosted service · you call their endpoint
  confidence: medium
  source:
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source:
  - security
  generated: '2026-11-13'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/onthemarket.png
tags:
- Real Estate
- United Kingdom
- Property Listings
- Property Portal
- PropTech
- Rentals
- Estate Agents
- Data Feed
- New Homes
- Commercial Real Estate
tags_raw:
- Real Estate
- United Kingdom
- Property Listings
- Property Portal
- PropTech
- Rentals
- Estate Agents
- Data Feed
- New Homes
- Commercial Real Estate
- Real-Estate
created: '2026-07-26'
modified: '2026-07-26'
specificationVersion: '0.23'
apis:
- aid: onthemarket:onthemarket-real-time-datafeed-api
  name: OnTheMarket Real Time Datafeed (RTDF) API
  description: 'OnTheMarket''s member-only feed API for estate-agency CRM software. It is modelled on the Rightmove Real Time
    Datafeed (RTDF/ADF) specification, with OnTheMarket-specific differences in request and response fields and an "Only With
    Us" capability for exclusive listings; overseas properties are not supported. The service host realtime-api.onthemarket.com
    is live and presents an OnTheMarket TLS certificate (subject O=Agents'' Mutual Limited, CN=*.onthemarket.com), and the
    enquiry endpoint /v1/property/getbranchemails is published in third-party CRM vendor setup instructions. OnTheMarket publishes
    no documentation, no OpenAPI, no Swagger and no OData $metadata for it: every path on the host returns HTTP 404 with an
    empty body to an anonymous client, and there is no self-service signup. Access requires an existing OnTheMarket agent
    membership with a data feed in place, arranged through OnTheMarket support — a Rightmove-style RTDF connection using a
    client certificate over TLS. Listed here as a real but undocumented and member-gated surface, with no machine-readable
    contract available to harvest.'
  humanURL: https://expert.onthemarket.com/contact-us/
  baseURL: https://realtime-api.onthemarket.com/v1
  tags:
  - Data Feed
  - Property Listings
  - Leads
  - Estate Agents
  properties:
  - type: Website
    url: https://expert.onthemarket.com/
  - type: Support
    url: https://expert.onthemarket.com/contact-us/
common:
- type: DomainSecurity
  url: security/onthemarket-domain-security.yml
- type: Conformance
  name: Standards conformance assessment (derived)
  url: conformance/onthemarket-conformance.yml
- type: Lifecycle
  name: Versioning, deprecation, SLA and status posture
  url: lifecycle/onthemarket-lifecycle.yml
- type: Packages
  name: Client-library survey (no first-party packages)
  url: packages/onthemarket-packages.yml
- type: LLMsTxt
  name: API Evangelist-generated llms.txt for OnTheMarket
  url: llms/onthemarket-llms.txt
- type: LLMsTxt
  name: OnTheMarket Expert llms.txt (published by OnTheMarket, saved verbatim)
  url: https://expert.onthemarket.com/llms.txt
- type: Website
  url: https://www.onthemarket.com/
- type: About
  url: https://www.onthemarket.com/about/
- type: TermsOfService
  url: https://www.onthemarket.com/terms/
- type: PrivacyPolicy
  name: Privacy notice (redirects to the CoStar Group global privacy notice)
  url: https://www.onthemarket.com/privacy/
- type: Blog
  url: https://www.onthemarket.com/content/
- type: BlogRSS
  url: https://www.onthemarket.com/content/feed/
- type: HelpCenter
  name: OnTheMarket Expert Help Centre (member-facing)
  url: https://expert.onthemarket.com/help-centre/
- type: Partners
  url: https://expert.onthemarket.com/our-partners/
- type: Support
  url: https://expert.onthemarket.com/contact-us/
- type: SignUp
  url: https://expert.onthemarket.com/join-us/
- type: Login
  url: https://expert.onthemarket.com/apps/login
- type: GitHubOrganization
  url: https://github.com/OnTheMarket
- type: LinkedIn
  url: https://www.linkedin.com/company/onthemarket/
- type: ParentCompany
  url: https://www.costargroup.com/
- type: UsageTerms
  url: terms/onthemarket-terms-of-service.yml
- type: Eligibility
  url: eligibility/onthemarket-eligibility.yml
- type: AIPreferences
  url: ai-preferences/onthemarket-ai-preferences.yml
- type: DataLicense
  url: data-license/onthemarket-data-license.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

OnTheMarket API — frequently asked questions

Does OnTheMarket have an API?

Yes. APIs.io lists 1 API from OnTheMarket, including OnTheMarket Real Time Datafeed (RTDF) API.

Is the OnTheMarket API ready for AI agents?

OnTheMarket has a Kin Score of 16.7 out of 100 (emerging) and an Agent Readiness score of 0.0 (human-only), scored by API Evangelist on 2026-11-13.

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