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A2A Home (Buildings & Contents) Agent Standard
Version: 1.0 (Draft for Comment)
Status: Working Draft, informed by a live carrier deployment
Steward: Marrow (onmarrow.com), on behalf of the Agent-to-Agent (A2A) working group
Line of business: UK residential home insurance (buildings, contents, combined)
Published: June 2026
This is a draft request for comment. It defines how an autonomous AI agent should request, compare, and transact a UK residential home insurance quote against a regulated carrier, safely, auditably, and carrier-agnostically. It is published openly so that carriers, agent platforms, and regulators can converge on one shape. Comments to standards@onmarrow.com.
Version note. This is published as v1.0 rather than an early draft because home buildings and contents is already running in production through the Marrow rail with a Tier-1 UK carrier. The field set and behavioural rules below are informed by that live deployment. The confidence note in the next section still applies: alignment to the exact Polaris and BCIS code lists requires licensed data access and is the step from v1.0 to v1.1.
Foundational dependency. This standard relies on the A2A Core Patterns Standard for all shared behavioural rules (grounding and no fabrication, assume-infer-confirm, the advice boundary, disclose-and-acknowledge, fair presentation, honest absence, data protection, vulnerability and Consumer Duty, handover machinery, and audit) and the canonical roles, and on the A2A Consent, Authority and Scopes Standard for authentication and transaction authority. Only the rules distinctive to home are stated in full below. The distinctive features of home are property-data enrichment keyed off the address, the rebuild-cost-not-market-value rule, and non-standard-construction and flood handling.
What is distinctive about home
Two things separate home from motor.
First, the enrichment key is the address (UPRN), not a personal identifier. From a resolved address, the rail can establish most of the property's physical characteristics, its rebuild cost, and its flood and subsidence exposure from authoritative property data, so the agent confirms rather than interrogates, exactly as in motor but keyed off the property.
Second, home carries a structural underinsurance risk that the standard must actively prevent. The buildings sum insured is the cost to rebuild the property, which is frequently very different from its market value, and customers routinely conflate the two. A conformant agent must derive the buildings sum insured from rebuild-cost data and explain the distinction, because getting it wrong is a Consumer Duty failure waiting to surface at claim.
Sources and provenance
- Address and UPRN resolution (Ordnance Survey AddressBase and equivalent) gives the Unique Property Reference Number that keys all subsequent property enrichment.
- Property data platforms return, by UPRN, property type, year built, construction type, roof type, number of bedrooms and bathrooms, listed-building status, conservation-area status, EPC data, outbuildings, and AVM valuation.
- BCIS (Building Cost Information Service), run under the ABI, is the principal UK source of residential rebuilding-cost data and supports the rebuild-cost calculation behind the buildings sum insured. BCIS recommends rebuild cost is rechecked at least every five years rather than index-linked indefinitely.
- Environment Agency flood-risk data establishes flood exposure, and Flood Re is the UK reinsurance scheme that makes flood cover affordable for eligible high-risk homes; the standard flags eligibility.
- EPC register corroborates age, construction, and energy characteristics.
- CUE (Claims and Underwriting Exchange) holds home claims as well as motor and is checked to verify claims, flood, subsidence, and landslip history.
- Polaris UK personal-lines code lists (via the Polaris Online Database) are the code lists the canonical schema aligns to.
- UK aggregator and insurer question sets (MoneySupermarket, Aviva, AXA, Nationwide, NFU Mutual and others) corroborate the customer-facing field list.
Confidence statement
Locked: the structure, the address-keyed enrichment model, the rebuild-cost rule, and the existence and role of every source above, corroborated across multiple carriers and against a live production deployment.
Not yet locked: the exact canonical code lists (property type, construction type, peril and cover enumerations) and the precise rebuild-cost integration require licensed access to Polaris POD and BCIS. v1.0 aligns to these conceptually and names them; v1.1 follows that access and the accumulated production data, at which point the standard can claim conformance rather than alignment.
1. Design principles
The shared design principles (carrier-agnostic by construction; look up, do not ask; no fabrication; assume-infer-confirm; disclose-and-acknowledge; observable compliance) are defined in the A2A Core Patterns Standard and apply in full. The principle distinctive to home:
Rebuild cost, not market value. The buildings sum insured is the cost to rebuild, derived from rebuild-cost data, and the agent must state the distinction to the customer and guard against the underinsurance that arises when the two are confused. Home also applies look up, do not ask keyed off the address (UPRN): property characteristics, rebuild cost, and flood and subsidence exposure are retrieved and confirmed, leaving the customer principally the contents sum insured and claims attestation.
Live demo
The same protocol, walked through interactively. The left panel is the agent's conversation; the right is the canonical home_quote_request building up, every value tagged with its provenance — enriched, attested, derived, or asked. Watch the rebuild-cost rule fire at step 2, and note that the Bind & pay action stays locked until all six conditions of the bind precondition invariant (defined in the New Business Standards) are met. Step through it:
2. Roles and terms
Roles and terms (Customer, Agent, Surface, Rail, Carrier, Material fact) are defined in the A2A Core Patterns Standard. Home-specific term: UPRN, the Unique Property Reference Number that keys property enrichment.
3. Canonical home quote request
The agent assembles a home_quote_request. Fields are marked enrichable (the rail can populate; the customer confirms), required (must be present or confirmed before a quote call), or conditional.
3.1 Property identifier (enrichment key)
| Field | Type | Notes |
|---|---|---|
property_address | enrichable key | Resolved to UPRN. Keys all property enrichment below. |
uprn | enrichable | Derived from the address; the join key for property data. |
3.2 Policyholder and occupancy
| Field | Required | Notes |
|---|---|---|
policyholder_dob | required | Rating factor. |
occupancy_status | required | Owner-occupied, let, second home, holiday home, unoccupied. Drives appetite and cover. |
residents | required | Who lives at the property; relevant to contents and liability. |
ownership | required | Owner, tenant (contents only), landlord. |
unoccupancy_periods | conditional | Regular periods the property is left unoccupied; a material exclusion trigger. |
3.3 Property characteristics (enriched from UPRN)
| Field | Required | Basis / notes |
|---|---|---|
property_type | enrichable | Detached, semi, terraced, flat, bungalow, maisonette. Property data. |
year_built | enrichable | Property data and EPC. |
bedrooms / bathrooms | enrichable | Property data. |
construction_standard | enrichable | Standard (brick or stone walls, tile or slate roof) versus non-standard. Property data, confirmed by customer. |
roof_type | enrichable | Pitched, flat, partial flat, thatch. |
listed_status / conservation_area | enrichable | Property data; affects rebuild cost and appetite. |
outbuildings | enrichable | Property data; relevant to buildings cover. |
3.4 Non-standard construction and hazards
| Field | Required | Basis / notes |
|---|---|---|
non_standard_features | required | Thatch, flat-roof proportion, timber or steel frame, non-standard cladding, underpinning, ongoing renovation. Partially hinted by enrichment, always confirmed. Non-standard features commonly route to referral (Section 6). |
flood_risk | enrichable | Environment Agency data. |
flood_re_eligibility | enrichable | Derived; flagged where the property is eligible for Flood Re. |
subsidence_history | required | From CUE and property data, confirmed by customer. |
security | required | Door locks (e.g. BS3621), window locks, alarm. Rating factor and warranty trigger. |
3.5 Sums insured
| Field | Required | Basis / notes |
|---|---|---|
buildings_sum_insured | enrichable | Derived from BCIS rebuild-cost data, not market value. The agent states the distinction. Basis: BCIS. |
contents_sum_insured | required | Estimated by the customer; the agent may offer a bedroom-based or property-based prompt but the figure is attested. |
high_value_items | conditional | Items above the single-article limit, specified individually. |
valuables_away_from_home | optional | Personal possessions cover away from the home. |
3.6 Claims and declarations
| Field | Required | Basis / notes |
|---|---|---|
claims_history | enrichable | Five-year, from CUE, confirmed by customer; includes flood, subsidence, landslip, escape of water, theft. Basis: CUE. |
previous_insurance_refused_cancelled_voided | required | Material, high non-disclosure risk. |
3.7 Cover requirements
| Field | Required | Notes |
|---|---|---|
cover_basis | required | Buildings only, contents only, or combined. |
voluntary_excess | required | |
accidental_damage | optional | Buildings and/or contents accidental damage. |
cover_start_date | required | |
addons | optional | Canonical list: home emergency, legal expenses, personal possessions, bicycle, tenants liability. |
4. Enrichment hooks
The rail performs these between request assembly and the carrier call. Results are returned for customer confirmation, never used silently.
| Hook | Source | Populates / checks | Basis |
|---|---|---|---|
address_uprn_resolve | OS AddressBase and equivalent | UPRN from address. | Address data |
property_characteristics | Property data platform | Type, year built, construction, roof, bedrooms, listed and conservation status, outbuildings, EPC. | Property data, EPC |
rebuild_cost | BCIS | Buildings sum insured by rebuild cost. | BCIS |
flood_risk | Environment Agency | Flood exposure and Flood Re eligibility flag. | EA, Flood Re |
subsidence_risk | Property and geological data | Subsidence exposure. | Property data |
claims_check | CUE | Claims, flood, subsidence, landslip history. | CUE |
postcode_risk | Postcode metadata | Crime and area risk context. | Aggregator convention |
A carrier may override any source with its own preferred vendor; canonical field names do not change.
5. Agent behavioural rules (compliance semantics)
The general behavioural rules (no fabrication, information-not-advice, material-fact confirmation, disclose-and-acknowledge, PII minimisation, fair presentation, honest absence) are defined in Core Patterns Section 2 and apply in full. Home-specific rules:
- Rebuild cost, not market value. The agent derives the buildings sum insured from rebuild-cost data, states the distinction, and actively guards against underinsurance. Where the customer asserts a figure materially below the rebuild-cost estimate, the agent surfaces the gap.
- Surface Flood Re and non-standard routes honestly. Where the property is high flood risk or non-standard, the agent explains the Flood Re position or the likelihood of specialist referral rather than implying standard cover exists.
- Material facts attested include non-standard construction, subsidence history, occupancy, unoccupancy periods, and the previous-insurance declaration; warranties acknowledged in-conversation include security warranties (for example required locks), thatch fire-precaution conditions, and any flood terms.
6. Canonical home quote response
The carrier (via the rail) returns a home_quote_response with zero or more quote objects. Zero quotes is valid and means no appetite, common for non-standard construction or high flood risk.
| Field | Notes |
|---|---|
carrier_quote_reference | Required for bind. |
annual_premium / monthly_premium | As returned; monthly implies a credit agreement with APR disclosed. The agent does not recompute. |
cover_basis | Buildings, contents, or combined. |
buildings_sum_insured / contents_sum_insured | As rated. |
compulsory_excess / voluntary_excess | Including any subsidence or escape-of-water specific excess. |
cover_features | Structured against a canonical home feature taxonomy (aligned to Defaqto) for like-for-like comparison. |
key_exclusions | Surfaced under disclose-and-acknowledge. |
warranties_conditions | Security, occupancy, thatch, and maintenance warranties; surfaced explicitly because breach affects cover. |
priced_addons | Each add-on priced separately. |
ipid_url | Insurance Product Information Document. |
validity_expires_at | |
appetite_status | quoted, declined, or referred. Non-standard and high-flood risks commonly refer; a referral routes to handover. |
7. Handover triggers
The shared handover machinery and common triggers are defined in Core Patterns Section 2.9. Home-specific triggers, additional to those: non-standard construction, listed buildings, subsidence history, or high flood risk causing all quotes to refer; an occupancy or property outside the schema's capacity; or a material attested fact conflicting with property enrichment in a way the agent cannot resolve.
8. Audit requirements
Audit requirements are defined in Core Patterns Section 2.10 and apply in full. Home-specific evidentiary emphasis: the rebuild-cost derivation and any underinsurance warning surfaced, and the warranties (security, occupancy, thatch, maintenance) acknowledged. This supports fair-value and underinsurance monitoring specific to home.
9. Versioning and conformance
This standard is versioned (v1.0) and relies on the A2A Core Patterns Standard and the A2A Consent, Authority and Scopes Standard; conformance requires conformance to those at a declared version. A conformant agent implements Sections 3 through 8 in full, including the rebuild-cost rule. A conformant carrier maps its home product to the canonical request and response. v1.1 follows Polaris POD and BCIS data access and accumulated production data, moving the standard from alignment with UK home data and rebuild-cost standards to conformance with them.
10. Open questions for comment
- Locking the canonical property type, construction, peril, and cover-feature code lists against Polaris POD and the rebuild-cost integration against BCIS.
- The contents-sum-insured prompt: how much the agent should estimate versus require the customer to attest, given underinsurance risk on contents as well as buildings.
- The threshold at which an underinsurance gap between customer figure and rebuild-cost estimate must trigger an explicit warning or block.
- How advised sales and any demands-and-needs assessment should be represented.
- Multi-carrier ordering disclosure minimums.
Published as an open standard. Marrow stewards the drafting but does not assert proprietary control over the interface; the compliance, enrichment, and audit implementations behind it are separate. Carriers, agent platforms, and regulators are invited to adopt, critique, and co-author future versions.