# Arthur Online

> Arthur Online is a London-headquartered UK property management platform (founded 2008, acquired by Aareon in January 2021) used by letting agents, self-managing landlords, block and social housing managers, and student accommodation operators. The Arthur API v2 is a JSON REST API over 317 documented operations across 16 resource areas, secured with OAuth 2.0 Authorization Code and scoped to an account by the mandatory X-EntityID header. Arthur publishes the complete API reference anonymously as a public Postman collection, but issues credentials only to paying accounts that ask support for access. There is no RESO posture: the UK has no MLS, no NAR and no RESO certification regime.

Generated by the API Evangelist enrichment pipeline on 2026-07-26. Method: generated from apis.yml plus the artifacts in this repository. Source of truth for the contract: https://developer.arthuronline.co.uk/

## Access at a glance

- Base URL: https://api.arthuronline.co.uk/v2 (401 to every anonymous request - there is no public read surface)
- Auth: OAuth 2.0 Authorization Code. Authorize https://auth.arthuronline.co.uk/oauth/authorize, token https://auth.arthuronline.co.uk/oauth/token
- Token lifetimes: authorization code 15 minutes, access token 14 days, refresh token 21 days
- Required on every call: `Authorization: Bearer <token>` and `X-EntityID: <entity_id>`; add `Content-Type: application/json` on POST/PUT
- Rate limit: 5,000 requests per hour, platform-wide; raise via Arthur technical support
- Getting credentials: be inside a paying Arthur account, ask Arthur support for API access, then register an application under Settings > OAuth Applications
- No scopes, no idempotency key, no sandbox, no SDKs, no CLI, no status page, no change log

## APIs

- [Arthur Properties API](https://developer.arthuronline.co.uk/): Properties and everything hung off them - assets, certificates, conversations, general information, notes, units, tenancies, tasks, work orders, utilities, transactions, tags
- [Arthur Units API](https://developer.arthuronline.co.uk/): Lettable units beneath a property, plus unit-level viewings, tenancies and compliance
- [Arthur Tenancies API](https://developer.arthuronline.co.uk/): Tenancy agreements, tenants on a tenancy, deposit registration, recurring charges
- [Arthur Tenants API](https://developer.arthuronline.co.uk/): Tenant people records and tenant-portal invitations
- [Arthur Applicants API](https://developer.arthuronline.co.uk/): The lettings funnel - applicant status, credit checks, assigned managers
- [Arthur Viewings API](https://developer.arthuronline.co.uk/): Viewing appointments, attached applicants, offers
- [Arthur Maintenance API](https://developer.arthuronline.co.uk/): The largest surface - tasks, subtasks, work orders, quotes, contractor workflow
- [Arthur Financials API](https://developer.arthuronline.co.uk/): Invoices, transactions, transaction payoff, recurring charges
- [Arthur Assets API](https://developer.arthuronline.co.uk/): Files and documents shared with owners, tenants and contractors
- [Arthur Utilities API](https://developer.arthuronline.co.uk/): Utility accounts and meter readings
- [Arthur Certificates API](https://developer.arthuronline.co.uk/): Compliance certificates with expiry tracking
- [Arthur Entities API](https://developer.arthuronline.co.uk/): The account boundary named in X-EntityID
- [Arthur Conversations API](https://developer.arthuronline.co.uk/): Threaded messaging between managers, tenants, owners and contractors
- [Arthur Tags API](https://developer.arthuronline.co.uk/): Cross-cutting tagging on every major record
- [Arthur Notes API](https://developer.arthuronline.co.uk/): Free-text notes on any record
- [Arthur Types API](https://developer.arthuronline.co.uk/): 39 read-only reference vocabularies backing every enumerated field

## Specs

- [OpenAPI 3.1 (16 documents, 317 operations)](openapi/): derived operation-for-operation from the provider's public Postman collection
- [AsyncAPI 3.0 webhooks](asyncapi/arthur-online-webhooks-asyncapi.yml): 125 subscribable triggers across 30 models
- [Webhook catalogue](asyncapi/arthur-online-webhooks.yml): triggers, delivery contract, envelope, official payload templates
- [Postman collection](collections/arthur-online.postman_collection.json): the provider's own published reference, 324 requests
- [OpenAPI overlays](overlays/): API Evangelist enhancements over each derived spec

## Runtime semantics

- [Conventions](conventions/arthur-online-conventions.yml): entity header, response envelope, pagination, filters, Simple types and `strict`, custom fields, data types, throttling
- [Authentication](authentication/arthur-online-authentication.yml): the OAuth 2.0 profile
- [Errors](errors/arthur-online-problem-types.yml): the proprietary {status, error, message} envelope and the documented 200/400/401/404 statuses
- [Rate limits](rate-limits/arthur-online-rate-limits.yml): 5,000 requests per hour
- [Lifecycle](lifecycle/arthur-online-lifecycle.yml): v2 URI versioning, no deprecation policy, no status page, commercial support terms
- [Data model](data-model/arthur-online-data-model.yml): the entity graph read from the nested path shapes
- [Vocabulary](vocabulary/arthur-online-vocabulary.yml): the 39 Types endpoints plus the core lettings terms
- [Conformance](conformance/arthur-online-conformance.yml): what Arthur does and does not conform to, including the absent RESO posture
- [Domain security](security/arthur-online-domain-security.yml): TLS, HSTS, SPF, DMARC probe results

## Agent surfaces

- [Candidate MCP tool surface](mcp/arthur-online-mcp.yml): 317 candidate tools derived from the operations - Arthur ships no hosted MCP server
- [Tool crosswalk](mcp/arthur-online-tool-crosswalk.yml): each candidate tool bound to its backing operation, plus the UI-only capabilities
- [Agent skills](skills/_index.yml): packaged operating instructions for the marquee flows
- [Agentic access](agentic-access/arthur-online-agentic-access.yml): recommended execution contracts per operation
- [Arazzo workflows](arazzo/_index.yml): multi-step flows stitched from real operationIds

## Agent cautions

- Writes are not idempotent and carry no request key. Never auto-retry a POST or PUT - it creates a duplicate record.
- Send `strict=true` on POST/PUT. Without it, an unrecognised Simple type value is silently created as new reference data in the customer's account.
- Resolve every enumerated value against the Types API before writing; do not guess enum members.
- Records are only visible inside the entity named in X-EntityID. A wrong entity id returns 404, not 403.
- Webhook deliveries are unsigned. Do not trust a payload without an out-of-band check against the API.
- The API host answers 401 to everything anonymous - there is nothing to explore without customer credentials.

## Docs

- [Developer portal / API reference](https://developer.arthuronline.co.uk/)
- [Postman Documenter](https://documenter.getpostman.com/view/22554870/2s93sZ5YeM)
- [Arthur API overview](https://www.arthuronline.co.uk/connect/arthur-api)
- [Integrations directory](https://www.arthuronline.co.uk/connect/)
- [Support portal / knowledge base](https://support.arthuronline.co.uk/)
- [API support and bespoke endpoint terms](https://support.arthuronline.co.uk/support/solutions/articles/202000052217-api-work-providing-support)
- [Pricing](https://www.arthuronline.co.uk/pricing)
- [Data security FAQs](https://www.arthuronline.co.uk/legal/data-security)
- [Fair usage policy](https://www.arthuronline.co.uk/legal/fair-usage-policy)
- [Privacy policy](https://www.arthuronline.co.uk/legal/privacy-policy)
- [Terms and conditions](https://www.arthuronline.co.uk/legal/terms-and-conditions)
- [GitHub organisation](https://github.com/arthur-crm)
- [Webhook payload templates](https://github.com/arthur-crm/webhookPayloadTemplates)