MarketCode

Energy rating, MEES and the retrofit gap

property_energy_retrofit

Read-onlyIdempotent

The energy picture for one property: current rating against the
certificate's own potential, the points and letter bands available, the
fabric and heating the assessor recorded, and MEES.

MEES IS A LEGAL BAR, NOT A VALUATION NOTE. An F or G cannot lawfully be let
on a new or continuing tenancy in England and Wales without a registered
exemption. Report it as a constraint on what the owner may do, not as a
discount to apply.

A band letter is a RANGE — G spans 19 SAP points, D spans 13 — and the
range is on the response. A null gap means unknown, never "already at
potential".

`recommended_measures` reads `not_available` (gap G3): the assessor's own
improvement list with indicative costs is published by MHCLG in a file we
do not load. Do NOT substitute a generic list of retrofit measures — it
would read as this property's assessment. No pound figure is put on the
uplift either; the elasticity is local and contested and we have not
estimated one.
UK only. Costs 5 credits (5p). Keyed on a UPRN, not an address: call `address_autocomplete` (free) to narrow, then `address_resolve` to get one.

Input Schema

Name	Required	Description	Default
`uprn`	Yes

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 29, 2026

TDQS

A4.3/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover readOnly/idempotent/non-destructive, and the description still adds substantial non-schema behaviour: a 5-credit (5p) cost, the meaning of a null gap ('unknown, never at potential'), a deliberate not_available state for recommended_measures with a reason (MHCLG file not loaded), and an explicit refusal to estimate a pound uplift. These are exactly the caveats an agent needs to avoid misreporting results.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The payload sentence is front-loaded and each block earns its place: the MEES legal framing, the band-as-range warning, the not_available caveat, and the access recipe. Some phrasing is rhetorical (capitalised prohibitions, 'the elasticity is local and contested'), which costs a little density but guards against real misuse.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need no explanation, and the description still covers the interpretive traps an agent would otherwise hit: band ranges, null gaps, the unavailable measures list, absent cost uplift, and how to obtain the UPRN. Nothing needed to call or correctly report on this tool is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 0% schema description coverage and a single untyped integer 'uprn', the description carries the burden and does: it states the key is a UPRN not an address, and gives the two-tool path to obtain one. It does not give the UPRN's format (e.g. 12-digit) or how to handle missing/ambiguous results, so it is strong but not exhaustive.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The first sentence names a specific resource (one property's energy picture) and enumerates the contents: current rating vs certificate potential, SAP points and letter bands, recorded fabric and heating, and MEES. That is more specific than a title restatement, but it never names the sibling it displaces (energy_profile, epc_certificates) so an agent must infer the boundary.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit prerequisites and routing: 'UK only', 'Keyed on a UPRN, not an address', plus the two-step recipe via free address_autocomplete then address_resolve. It also constrains interpretation ('report MEES as a constraint on what the owner may do, not as a discount'). It stops short of stating when to prefer this over energy_profile or epc_certificates.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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