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.
Solid contracts, transparent operations, and an easy start — typically complete on four or five facets with one clear soft spot.
API Evangelist profiles Arthur Online the way a machine reads it — 28 machine-readable artifacts across 16 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 63.6/100 (strong), with a separate agent-readiness read of 85/100 (agent native). 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.
Kin Score
How this is scored →scored 2026-07-27 · rubric v0.5
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 16
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 Properties API
Property records and everything hung off a property in Arthur - assets, certificates, conversations, general information, notes, units, tenancies, tasks, work orders, utilities,...
Arthur Units API
Individual lettable units beneath a property, plus the unit-level assets, certificates, conversations, notes, viewings, tenancies, tasks, work orders, utilities, transactions an...
Arthur Tenancies API
Tenancy agreements over a unit, including tenants on the tenancy, deposit registration, recurring charges, certificates, tasks, work orders, conversations, transactions, notes a...
Arthur Tenants API
Tenant people records - list, view, create and update tenants, and invite a tenant into the Arthur tenant portal. 3 documented paths.
Arthur Applicants API
Prospective renters moving through the lettings funnel, including applicant status, credit checks, managers, assets, conversations, notes, tasks and tags. 15 documented paths.
Arthur Viewings API
Property and unit viewing appointments, the applicants attached to each viewing, assigned managers, conversations, notes and tags. 15 documented paths.
Arthur Maintenance API
The largest surface in the API - tasks, subtasks, work orders, quotes and the contractor workflow around them. 45 documented paths.
Arthur Financials API
Rental financials - invoices, transactions, transaction payoff and recurring charges. Read and update only; no create operations are documented. 6 documented paths.
Arthur Assets API
Files and documents stored in Arthur and shared with owners, tenants and contractors. 2 documented paths.
Arthur Utilities API
Utility accounts attached to properties and units, and the meter readings recorded against them. 4 documented paths.
Arthur Certificates API
Compliance certificates - gas safety, electrical, EPC and similar - with expiry tracking that also drives webhook events at 30 days, 7 days and on the day. 2 documented paths.
Arthur Entities API
Arthur entities - the account boundary that every API call must name in the mandatory X-EntityID request header. 2 documented paths.
Arthur Conversations API
Threaded conversations and messages between managers, tenants, owners and contractors, with attached assets. 4 documented paths.
Arthur Tags API
Cross-cutting tags applied to properties, units, tenancies, applicants, viewings and notes, with tag and untag operations on each resource. 2 documented paths.
Arthur Notes API
Free-text notes recorded against any Arthur resource, with their own tagging operations. 5 documented paths.
Arthur Types API
Read-only reference vocabularies backing every enumerated field in Arthur - access detail types, applicant statuses and types, area types, asset types, certificate types, citize...
Scroll within the panel for all 16 ·
Arazzo Workflows 4
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.
_Index
ARAZZOArthur 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 ...
ARAZZOMCP Servers 1
Model Context Protocol servers expose these APIs directly to AI agents. We profile them because agent-native access is the fastest-growing way this provider's capabilities actually get used.
Model Context Protocol servers that expose these APIs to AI agents.
arthur-online-mcp.yml
MCP SERVERPricing 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 six things the Kin Score reads for commercial clarity.
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 6
SDKs, sample code, and the tooling you integrate with
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
← All providers · Data indexed from github.com/api-evangelist/arthur-online · machine-readable index on apis.io