/zoning-analysis-nyc — Zoning Envelope Analysis (New York City)

Analyze building envelope rules for any lot in New York City using the PLUTO database (NYC Open Data) and the NYC Zoning Resolution.

Workflow

Step 1: Parse Input

Accept one of the following identifiers:

• Address + Borough/Zip — e.g., "123 Main St, Brooklyn 11201"
• BBL — 10-digit Borough-Block-Lot (e.g., 3012340056 = Brooklyn, Block 1234, Lot 56)
• BIN — Building Identification Number

Normalize to BBL format: [borough 1 digit][block 5 digits][lot 4 digits]

Borough codes:

Step 2: Query PLUTO (tabular + polygon)

Fetch lot data from two NYC APIs in parallel:

2a. Tabular data (Socrata PLUTO)

Endpoint: https://data.cityofnewyork.us/resource/64uk-42ks.json

Query by BBL:

https://data.cityofnewyork.us/resource/64uk-42ks.json?bbl=XXXXXXXXXX

Query by address (fallback):

https://data.cityofnewyork.us/resource/64uk-42ks.json?$where=address='123 MAIN STREET' AND zipcode='10001'

No authentication required for basic queries.

Read zoning-rules/pluto-fields.md for the full field reference.

Extract these key fields:

• bbl — Borough-Block-Lot
• address, zipcode — street address
• zonedist1 through zonedist4 — zoning district(s)
• overlay1, overlay2 — commercial overlay districts
• spdist1, spdist2, spdist3 — special purpose districts
• ltdheight — limited height district
• splitzone — Y if lot is split across zones
• lotarea — lot area in SF
• bldgarea — total building area in SF
• builtfar — as-built FAR
• residfar — maximum residential FAR
• commfar — maximum commercial FAR
• facilfar — maximum community facility FAR
• numfloors — existing number of floors
• landuse — current land use category
• zonemap — zoning map number
• landmark — landmark designation
• histdist — historic district name
• borocode, block, lot — parsed BBL components

2b. Lot polygon (MapPLUTO ArcGIS Feature Service)

Endpoint: https://a841-dotweb01.nyc.gov/arcgis/rest/services/GAZETTEER/MapPLUTO/MapServer/0/query

Query by BBL:

https://a841-dotweb01.nyc.gov/arcgis/rest/services/GAZETTEER/MapPLUTO/MapServer/0/query?where=BBL='XXXXXXXXXX'&outFields=BBL&f=json&outSR=4326

This returns the exact tax lot polygon in WGS84 (lat/lon). No authentication required.

Convert to local feet:

1. Extract the features[0].geometry.rings[0] coordinate array (pairs of [lon, lat])
2. Compute the centroid latitude for the cos correction factor: cos(lat)
3. Convert to local feet using:
   • x_ft = (lon - lon_min) × 111320 × cos(lat) × 3.28084
   • y_ft = (lat - lat_min) × 111320 × 3.28084
4. Origin at the southernmost point (Y=0 at street/south side)
5. Output a LOT_POLY array of [x, y] pairs in feet
6. Verify the computed area against PLUTO's lotarea (expect ±5% due to projection)

Always use the real polygon for the 3D envelope viewer. Never fall back to a lotfront × lotdepth rectangle when polygon data is available.

If either query returns no results, inform the user and ask them to verify the address or BBL.

Step 3: Identify Zoning District

Map the zonedist1 value to its district type:

Check for:

• Split zones (splitzone = Y): Analyze each zonedist1–zonedist4 separately. Pro-rate FAR by estimated area in each zone if lot dimensions are available, otherwise present both sets of controls.
• Contextual suffixes (A, B, D, X): If the district code ends in a letter suffix (e.g., R7A, C6-2A), also load zoning-rules/contextual-districts.md.
• Commercial overlays (overlay1/overlay2): If present (e.g., C1-4, C2-5), load zoning-rules/commercial.md for overlay rules.
• Special districts (spdist1–spdist3): If present, load zoning-rules/special-districts.md.
• Limited height (ltdheight): Note the height cap.

State your district identification and reasoning clearly.

Step 4: Load Normativa

Read the relevant regulation files from the skill's zoning-rules/ directory:

1. Always read: zoning-rules/overview.md — system primer
2. Primary district file: One of residential.md, commercial.md, or manufacturing.md
3. Conditionally read:
   • zoning-rules/contextual-districts.md — if district has A/B/D/X suffix
   • zoning-rules/special-districts.md — if spdist1–spdist3 are populated
   • zoning-rules/use-groups.md — for permitted use analysis
   • zoning-rules/parking.md — for parking requirements
   • zoning-rules/city-of-yes.md — for recent reform impacts

Step 5: Determine Bulk Controls

Calculate the building envelope for the lot:

1. Floor Area Ratio (FAR):

   • Residential FAR (from residfar or district table)
   • Commercial FAR (from commfar or district table)
   • Community Facility FAR (from facilfar or district table)
   • Maximum zoning floor area = FAR × lot area

2. Building Height:

   • Base height range (contextual districts)
   • Maximum building height
   • Sky exposure plane angle and setback distance
   • Limited height district cap (if applicable)

3. Setbacks:

   • Front: initial setback distance and sky exposure plane
   • Side: narrow/wide street rules
   • Rear: standard 30 ft for residential, varies for commercial
   • Sky exposure plane: ratio and starting height

4. Lot Coverage:

   • Maximum lot coverage percentage
   • Open space ratio (for non-contextual R districts)

5. Yards:

   • Front yard requirements
   • Side yard requirements (corner lots, through lots)
   • Rear yard: typically 30 ft or 20% of lot depth

Apply contextual district rules when suffix is present — these override standard height/setback rules with mandatory streetwall, base height, and setback requirements.

Step 6: Check Overlays & Special Districts

Layer additional regulations on top of base district controls:

1. Commercial overlays (C1-1 through C2-5 in residential districts):

   • Additional commercial FAR (typically 1.0 or 2.0)
   • Commercial use depth limit (typically 150 ft from street)
   • Permitted commercial uses (Use Groups 5–9 for C1, 5–14 for C2)

2. Special purpose districts:

   • Modified bulk controls, use restrictions, design requirements
   • Check zoning-rules/special-districts.md for the specific district

3. Inclusionary Housing:

   • Bonus FAR available in designated areas
   • Mandatory Inclusionary Housing (MIH) areas: must provide affordable units for bonus

4. Landmark / Historic District:

   • If landmark or histdist is populated, note that Landmarks Preservation Commission (LPC) review is required
   • Bulk controls still apply but modifications may need LPC approval

5. City of Yes reforms:

   • Check zoning-rules/city-of-yes.md for applicable changes
   • Universal Affordability Preference (UAP): +20% FAR for affordable housing
   • Town Center Zoning: ground-floor commercial in residential districts near transit
   • Parking: most mandates eliminated citywide

Step 7: Present Analysis

Use the output format below to present a structured, comprehensive analysis.

Step 8: Save Report

Write the analysis to a markdown file in the current working directory:

• Filename: zoning-analysis-[address-slug].md
• Example: zoning-analysis-123-main-st-brooklyn.md

Output Format

# Zoning Analysis — [Address], [Borough]

## Lot Summary
| Parameter | Value |
|-----------|-------|
| BBL | X-XXXXX-XXXX |
| Address | ... |
| Borough | ... |
| Lot Area | ... SF |
| Current Building Area | ... SF |
| Current FAR (built) | ... |
| Current Use | .