Comparative Market Analysis

Comparative Market Analysis (CMA)

Overview

Estimate what a property is worth by triangulating three sources: comparable sales, the portal valuation/estimate, and local market trends. Produce a value range with explicit reasoning — not a single magic number.

Use [realtyapi-api](../realtyapi-api/SKILL.md) for auth and endpoint discovery. This skill builds on property-research (subject details) and adds rigor on comps.

When to Use

• "What should I list this house for?"
• "Run a CMA on 123 Main St."
• "What are the comps and what's it worth?"
• Pre-listing pricing, offer strategy, or a sanity check on an asking price.

Workflow

1. Subject property — fetch full details by address/URL (beds, baths, size, lot,

year, condition signals). This anchors the comparison.

1. Comparables — pull comps/similar/nearby sold homes. Filter to genuinely

comparable ones: similar size (±~15–20%), type, and recent sales (ideally last 3–6 months) in the same area. Drop outliers and explain why.

1. Portal valuation — pull the estimate/valuation (zestimate*, estimates).
2. Market trend — pull area market data (housing_market, market*,

housingMarketTrends): direction and $/sqft trend.

1. Derive the range — base it on comp $/sqft applied to the subject's size,

cross-checked against the portal estimate, then nudge for trend and condition. Present a low–high range and a most-likely figure.

1. Show your work in the report.

Output Format

# CMA: {address}

Subject: {beds}bd/{baths}ba · {size} sqft · {type} · built {year} · {source/link}

## Estimated Value
**{low} – {high}**  (most likely: {point})
- Basis: comp median $/sqft {x} × {size} sqft, adjusted for {trend/condition}
- Portal estimate (cross-check): {value} ({source})

## Comparable Sales
| Address | Sold | Price | Beds/Baths | Size | $/sqft | Dist | Adj. notes |
|---------|------|------:|-----------|-----:|-------:|-----:|-----------|

## Market Context
- Trend: {rising/flat/falling} · Median $/sqft: {} · Days on market: {}

## Confidence & Caveats
- Confidence: {high/med/low} — {# of comps, recency, dispersion}
- Not an appraisal; based on public data and model estimates.

Common Pitfalls

• Reject bad comps (wrong size/type, stale sales, different sub-market) — quality

over quantity. State how many comps survived.

• Don't blindly trust the portal estimate; use it as a cross-check, not the answer.
• Always give a range; flag low confidence when comps are thin or scattered.
• Use sold prices for comps, not active list prices, where possible.
• This is a CMA, not a licensed appraisal — say so.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: realtyapi
• Source: realtyapi/realtyapi-skills
• License: MIT

Install and usage instructions live in the source repository linked above.