GPT-5.5 vs Kimi K3 for property and lettings admin
GPT-5.5 wins, 94–90
Same 12 property and lettings admin tasks, marked blind by three rival labs. GPT-5.5 took 5 tasks, Kimi K3 took 2, 5 tied. Tested 18 Aug 2026.
Where they differed most
Guidance excerpt: 'A landlord is responsible for repairs to the structure and exterior of the property and to the installations for the supply of water, gas and electricity, for sanitation, and for space heating and heating water. Repairs should be carried out within a reasonable time, and what is reasonable depends on how serious the problem is and its effect on the tenant. Loss of heating or hot water is generally treated as urgent, particularly in cold weather or where a tenant is vulnerable. Tenants should report problems in writing and landlords should keep a record of what was reported and when.' Three reports arrive on the same Tuesday in November. (a) No hot water at all in a flat let to a tenant in her eighties. (b) A dripping kitchen tap. (c) A bannister that has come loose from the wall on the stairs. Answer using only the excerpt — marked against it. Triage the three, saying for each what makes it urgent or not by reference to the excerpt, what the agent does today, and what the agent tells the tenant today. Say which of the three the excerpt does not clearly cover and what you would do about that rather than guessing.
### Triage based only on the excerpt | Report | Urgency under the excerpt | What the agent does today | What the agent tells the tenant today | |---|---|---|---| | **(a) No hot water at all in a flat let to a tenant in her eighties** | **Urgent.** The excerpt says the landlord is responsible for installations for **heating water**. It also says **loss of hot water is generally urgent**, especially in **cold weather** or where the tenant is **vulnerable**. Here it is November and the tenant is in her eighties. | Log the report in writing with t…
**Triage order: (a) first, (c) second, (b) last.**
### (a) No hot water — tenant in her eighties — URGENT
- **Why urgent (per excerpt):** Hot water is squarely within the landlord's responsibility ("installations for... heating water"). The excerpt says loss of hot water is "generally treated as urgent, particularly in cold weather or where a tenant is vulnerable." Both factors apply here: it's November (cold weather) and the tenant is in her eighties (vulnerable). This is the clearest urgent case of the three.
- **Agent does today:** Record…Task by task
| Task | GPT-5.5 | Kimi K3 |
|---|---|---|
| Two routes, one worried tenant | 10 | 9 |
| Six weeks late and hoping | 8 | 9 |
| Write only the arrears email | 10 | 10 |
| The pre-tenancy checklist | 9 | 10 |
| Write only the renewal reply | 10 | 10 |
| Three repairs, one Tuesday | 10 | 8 |
| The nine-year-old carpet | 8 | 8 |
| The rent rise by text message | 9 | 8 |
| Every claim in the advert must be true | 9 | 9 |
| The compliance data, as JSON | 10 | 10 |
| What the agent must not promise | 10 | 8 |
| Refuse the lock change | 10 | 9 |
Full receipts: GPT-5.5, Kimi K3 · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5
Questions people ask
Which is better for property and lettings admin: GPT-5.5 or Kimi K3?
GPT-5.5 — it scored 94/100 against 90/100 on our 12-task property and lettings admin suite, winning 5 tasks to 2 with 5 tied. Every answer was marked blind by three judges from three rival AI labs.
How was this tested?
Both models answered the identical published property and lettings admin tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.
More property and lettings admin head-to-heads: GPT-5.5 vs GPT-5.6 Sol · Claude Opus 4.8 vs GPT-5.5 · Claude Fable 5 vs GPT-5.5 · Claude Sonnet 5 vs GPT-5.5 · GPT-5.5 vs Grok 4.5 · Gemini 3.1 Pro Preview vs GPT-5.5
Full ranking: Best AI for property and lettings admin · model pages: GPT-5.5, Kimi K3