Arthur Online
Arthur Online is a London-headquartered UK property management software platform, founded in 2008 and acquired by Aareon in January 2021, that gives letting agents, self-managing landlords, block and social housing managers, and student accommodation operators a cloud system of record for properties, units, tenancies, tenants, applicants, viewings, maintenance work orders, certificates, utilities and rental financials, with companion mobile apps for managers, tenants, contractors and owners. It sits in the middle of the UK residential lettings value chain: it is the agency-side operational system that pushes stock out to the Rightmove and Zoopla portals and pulls accounting into Xero and QuickBooks, rather than a listings marketplace or a data cooperative. Its API posture is unusually open for the sector but is not open data: the full Arthur API v2 reference is published without a login as a public Postman collection at developer.arthuronline.co.uk covering 324 documented requests across 16 resource areas, yet every call is tenant-scoped OAuth 2.0 Authorization Code plus an X-EntityID header, credentials are issued only from inside a paying Arthur account after contacting Arthur support, and no data is readable anonymously. There is no RESO posture at all — the United Kingdom has no MLS, no NAR, and no RESO Data Dictionary or Web API certification regime, so listings interoperability here is portal-to-CRM feeds rather than a certified machine-readable standard.
Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.
API Evangelist profiles Arthur Online the way a machine reads it — 74 machine-readable artifacts across 32 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.
Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Arthur Online scores 47.9/100 (developing), with a separate agent-readiness read of 38/100 (agent ready). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.
Kin Score
This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance. Every facet and dimension name is a link: it opens that measurement's page on APIs.io, where the rating runs across the whole catalog — the exact checks that feed it, how every profiled provider distributes on it, and who is at the top of it.
Kin Score
How this is scored →scored 2026-09-10 · rubric v0.20.0
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How we profile Arthur Online
Each block below is one kind of artifact we hold for Arthur Online. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.
APIs 32
Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.
Individual APIs this provider publishes, each with its own machine-readable definition.
Arthur Online Applicant API
The Applicant API from Arthur Online — 5 operation(s) for applicant.
Arthur Online Applicants API
The Applicants API from Arthur Online — 4 operation(s) for applicants.
Arthur Online Assets API
The Assets API from Arthur Online — 7 operation(s) for assets.
Arthur Online Assigned Managers API
The Assigned Managers API from Arthur Online — 4 operation(s) for assigned managers.
Arthur Online Certificates API
The Certificates API from Arthur Online — 5 operation(s) for certificates.
Arthur Online Contractor Invoices API
The Contractor Invoices API from Arthur Online — 2 operation(s) for contractor invoices.
Arthur Online Conversations API
The Conversations API from Arthur Online — 11 operation(s) for conversations.
Arthur Online Credit Checks API
The Credit Checks API from Arthur Online — 1 operation(s) for credit checks.
Arthur Online Entities API
The Entities API from Arthur Online — 2 operation(s) for entities.
Arthur Online General Information API
The General Information API from Arthur Online — 2 operation(s) for general information.
Arthur Online Invite API
The Invite API from Arthur Online — 1 operation(s) for invite.
Arthur Online Messages API
The Messages API from Arthur Online — 2 operation(s) for messages.
Arthur Online Notes API
The Notes API from Arthur Online — 12 operation(s) for notes.
Arthur Online Offers API
The Offers API from Arthur Online — 1 operation(s) for offers.
Arthur Online Properties API
The Properties API from Arthur Online — 2 operation(s) for properties.
Arthur Online Property API
The Property API from Arthur Online — 1 operation(s) for property.
Arthur Online Quotes API
The Quotes API from Arthur Online — 2 operation(s) for quotes.
Arthur Online Readings API
The Readings API from Arthur Online — 2 operation(s) for readings.
Arthur Online Recurrings API
The Recurrings API from Arthur Online — 2 operation(s) for recurrings.
Arthur Online Register Deposit API
The Register Deposit API from Arthur Online — 1 operation(s) for register deposit.
Arthur Online Subtasks API
The Subtasks API from Arthur Online — 2 operation(s) for subtasks.
Arthur Online Tags API
The Tags API from Arthur Online — 21 operation(s) for tags.
Arthur Online Task API
The Task API from Arthur Online — 3 operation(s) for task.
Arthur Online Tasks API
The Tasks API from Arthur Online — 26 operation(s) for tasks.
Arthur Online Tenancies API
The Tenancies API from Arthur Online — 5 operation(s) for tenancies.
Arthur Online Tenants API
The Tenants API from Arthur Online — 3 operation(s) for tenants.
Arthur Online Transactions API
The Transactions API from Arthur Online — 6 operation(s) for transactions.
Arthur Online Types API
The Types API from Arthur Online — 31 operation(s) for types.
Arthur Online Units API
The Units API from Arthur Online — 3 operation(s) for units.
Arthur Online Utilities API
The Utilities API from Arthur Online — 4 operation(s) for utilities.
Arthur Online Viewings API
The Viewings API from Arthur Online — 5 operation(s) for viewings.
Arthur Online Workorders API
The Workorders API from Arthur Online — 29 operation(s) for workorders.
Scroll within the panel for all 32 ·
Postman Collections 16
A runnable collection turns the contract into something a developer can execute in seconds. We profile them because the fastest way to trust an API is to make a real call against it.
Ready-to-run Postman collections for exercising this provider's APIs.
Arthur Applicants API
POSTMANArthur Assets API
POSTMANArthur Certificates API
POSTMANArthur Conversations API
POSTMANArthur Entities API
POSTMANArthur Financials API
POSTMANArthur Maintenance API
POSTMANArthur Notes API
POSTMANArthur Properties API
POSTMANArthur Tags API
POSTMANArthur Tenancies API
POSTMANArthur Tenants API
POSTMANArthur Types API
POSTMANArthur Units API
POSTMANArthur Utilities API
POSTMANArthur Viewings API
POSTMANScroll within the panel for all 16 ·
Open Collections 16
Open, tool-agnostic collections carry the same runnable value as Postman without locking you to one client — the portable, forkable form of the same exercise.
Open, tool-agnostic API collections (OpenAPI-derived and Bruno).
Arthur Applicants API
OPEN COLLECTIONArthur Assets API
OPEN COLLECTIONArthur Certificates API
OPEN COLLECTIONArthur Conversations API
OPEN COLLECTIONArthur Entities API
OPEN COLLECTIONArthur Financials API
OPEN COLLECTIONArthur Maintenance API
OPEN COLLECTIONArthur Notes API
OPEN COLLECTIONArthur Properties API
OPEN COLLECTIONArthur Tags API
OPEN COLLECTIONArthur Tenancies API
OPEN COLLECTIONArthur Tenants API
OPEN COLLECTIONArthur Types API
OPEN COLLECTIONArthur Units API
OPEN COLLECTIONArthur Utilities API
OPEN COLLECTIONArthur Viewings API
OPEN COLLECTIONScroll within the panel for all 16 ·
Arazzo Workflows 3
Real integrations are rarely a single call. Arazzo describes the multi-step sequences — auth, then create, then confirm — so both a human and an agent can follow the choreography, not just the endpoints.
Multi-step API workflows described with the Arazzo specification.
Arthur Online - applicant to tenancy
The UK lettings funnel in Arthur Online: confirm the entity, create an applicant, book a viewing on a unit, record the offer, convert the viewing into a tenancy, add the tenant ...
ARAZZOArthur Online - maintenance dispatch
Raise a maintenance task against a property, break it into subtasks, dispatch it to a contractor as a work order, open the conversation and read back quotes and invoices. Approv...
ARAZZOArthur Online - onboard a property
Bring a new building into Arthur Online: create the property, add a lettable unit, file the compliance certificate, publish the information shared with occupants and attach the ...
ARAZZOPricing Plans 1
Pricing is part of the interface. Machine-readable plans tell you what a tier costs and includes before you commit — one of the things the Kin Score reads for access clarity — renamed from commercial clarity in rubric 0.12, because a free statutory interface has access terms and no commercial ones.
Published pricing tiers and plan structures.
Arthur Online Plans
PLANSRate Limits 1
Rate limits are the difference between a demo that works and a production integration that doesn't fall over. Publishing them is an operational-transparency signal — and a hard requirement for any agent that plans its own throughput.
Documented rate limits and quota policies.
Arthur Online Rate Limits
RATE LIMITSEvent Specifications 2
Not every API is request/response. AsyncAPI describes the event-driven and streaming side — the webhooks and channels — so the asynchronous half of the interface is documented the same way the synchronous half is.
AsyncAPI definitions for this provider's event-driven and streaming APIs.
Arthur Online Webhooks
The Arthur Online webhook event surface. A property manager subscribes a webhook URL to one or more of the 125 published triggers on the Arthur webhook page; Arthur then POSTs a...
ASYNCAPIArthur Online Webhooks
ASYNCAPISecurity Posture 2
Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.
Authentication, domain security, vulnerability disclosure, and trust-center signals.
Agentic Access 1
An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.
Recommended x-agentic-access execution contracts for AI agents.
Resources
Every other property we hold for Arthur Online — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.
Get Started 6
Portal, sign-up, and the first successful call
Documentation 3
Reference material describing how the API behaves
Agent Surfaces 4
MCP servers, agent skills, and machine-readable catalogs
Design & Contract 8
Pagination, idempotency, versioning, errors, and events
Scroll within the panel for all 8 ·
Build 7
SDKs, sample code, and the tooling you integrate with
Scroll within the panel for all 7 ·
Access & Security 2
Authentication, authorization, and security posture
Operate 3
Status, limits, changes, and where to get help
Commercial 4
Pricing, plans, and the legal terms of use
Company 2
The organization behind the API
Other 16
Properties that don't map to a standard resource type
Scroll within the panel for all 16 ·
← All providers · Data indexed from github.com/api-evangelist/arthur-online · machine-readable index on apis.io
This is an independent, third-party profile of Arthur Online, published by API Evangelist. We do not operate, host, resell, or support these APIs, and we are not affiliated with or endorsed by the company unless stated above. Everything here is built from publicly available information — the company's own site, developer portal, documentation, public repositories, and the specifications it publishes for public use. Nothing is obtained by breaching a system, defeating an access control, or using credentials.
The Kin Score and Agent Readiness rating are independently calculated assessments of a company's public API artifacts, scored against a published rubric. They are not certifications, endorsements, security assessments, or audits.
Corrections, re-scores, and removal are free — no partnership or purchase required, and you do not need to justify the request. A removed company is recorded as unrated, never scored zero for having asked. Acknowledgement within one business day; removal within two.
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