gh-policyengine-policyengine-claude/skills/technical-patterns/policyengine-parameter-patterns-skill/SKILL.md

name, description

name	description
policyengine-parameter-patterns	PolicyEngine parameter patterns - YAML structure, naming conventions, metadata requirements, federal/state separation

PolicyEngine Parameter Patterns

Comprehensive patterns for creating PolicyEngine parameter files.

Critical: Required Structure

Every parameter MUST have this exact structure:

description: [One sentence description].
values:
  YYYY-MM-DD: value

metadata:
  unit: [type]       # REQUIRED
  period: [period]   # REQUIRED
  label: [name]      # REQUIRED
  reference:         # REQUIRED
    - title: [source]
      href: [url]

Missing ANY metadata field = validation error

---

1. File Naming Conventions

Study Reference Implementations First

Before naming, examine:

• DC TANF: /parameters/gov/states/dc/dhs/tanf/
• IL TANF: /parameters/gov/states/il/dhs/tanf/
• TX TANF: /parameters/gov/states/tx/hhs/tanf/

Naming Patterns

Dollar amounts → /amount.yaml

income/deductions/work_expense/amount.yaml     # $120
resources/limit/amount.yaml                    # $6,000
payment_standard/amount.yaml                   # $320

Percentages/rates → /rate.yaml or /percentage.yaml

income_limit/rate.yaml                         # 1.85 (185% FPL)
benefit_reduction/rate.yaml                    # 0.2 (20%)
income/disregard/percentage.yaml               # 0.67 (67%)

Thresholds → /threshold.yaml

age_threshold/minor_child.yaml                 # 18
age_threshold/elderly.yaml                     # 60
income/threshold.yaml                          # 30_000

---

2. Description Field

The ONLY Acceptable Formula

description: [State] [verb] [category] to [this X] under the [Full Program Name] program.

Components:

1. [State]: Full state name (Indiana, Texas, California)
2. [verb]: ONLY use: limits, provides, sets, excludes, deducts, uses
3. [category]: What's being limited/provided (gross income, resources, payment standard)
4. [this X]: ALWAYS use generic placeholder
   • this amount (for currency-USD)
   • this share or this percentage (for rates/percentages)
   • this threshold (for age/counts)
5. [Full Program Name]: ALWAYS spell out (Temporary Assistance for Needy Families, NOT TANF)

Copy These Exact Templates

For income limits:

description: [State] limits gross income to this amount under the Temporary Assistance for Needy Families program.

For resource limits:

description: [State] limits resources to this amount under the Temporary Assistance for Needy Families program.

For payment standards:

description: [State] provides this amount as the payment standard under the Temporary Assistance for Needy Families program.

For disregards:

description: [State] excludes this share of earnings from countable income under the Temporary Assistance for Needy Families program.

Description Validation Checklist

Run this check on EVERY description:

# Pseudo-code validation
def validate_description(desc):
    checks = [
        desc.count('.') == 1,  # Exactly one sentence
        'TANF' not in desc,     # No acronyms
        'SNAP' not in desc,     # No acronyms
        'this amount' in desc or 'this share' in desc or 'this percentage' in desc,
        'under the' in desc and 'program' in desc,
        'by household size' not in desc,  # No explanatory text
        'based on' not in desc,           # No explanatory text
        'for eligibility' not in desc,    # Redundant
    ]
    return all(checks)

CRITICAL: Always spell out full program names in descriptions!

---

3. Values Section

Format Rules

values:
  2024-01-01: 3_000    # Use underscores
  # NOT: 3000

  2024-01-01: 0.2      # Remove trailing zeros
  # NOT: 0.20 or 0.200

  2024-01-01: 2        # No decimals for integers
  # NOT: 2.0 or 2.00

Effective Dates

Use exact dates from sources:

# If source says "effective July 1, 2023"
2023-07-01: value

# If source says "as of October 1"
2024-10-01: value

# NOT arbitrary dates:
2000-01-01: value  # Shows no research

Date format: YYYY-MM-01 (always use 01 for day)

---

4. Metadata Fields (ALL REQUIRED)

unit

Common units:

• currency-USD - Dollar amounts
• /1 - Rates, percentages (as decimals)
• month - Number of months
• year - Age in years
• bool - True/false
• person - Count of people

period

• year - Annual values
• month - Monthly values
• day - Daily values
• eternity - Never changes

label

Pattern: [State] [PROGRAM] [description]

label: Montana TANF minor child age threshold
label: Illinois TANF earned income disregard rate
label: California SNAP resource limit

Rules:

• Spell out state name
• Abbreviate program (TANF, SNAP)
• No period at end

reference

Requirements:

1. At least one source (prefer two)
2. Must contain the actual value
3. Legal codes need subsections
4. PDFs need page anchors

✅ GOOD:
reference:
  - title: Idaho Admin Code 16.05.03.205(3)
    href: https://adminrules.idaho.gov/rules/current/16/160503.pdf#page=14
  - title: Idaho LIHEAP Guidelines, Section 3, page 8
    href: https://healthandwelfare.idaho.gov/guidelines.pdf#page=8

❌ BAD:
reference:
  - title: Federal LIHEAP regulations  # Too generic
    href: https://www.acf.hhs.gov/ocs  # No specific section

---

5. Federal/State Separation

Federal Parameters

Location: /parameters/gov/{agency}/{program}/

# parameters/gov/hhs/fpg/first_person.yaml
description: HHS sets this amount as the federal poverty guideline for one person.

State Parameters

Location: /parameters/gov/states/{state}/{agency}/{program}/

# parameters/gov/states/ca/dss/tanf/income_limit/rate.yaml
description: California uses this multiplier of the federal poverty guideline for TANF income eligibility.

---

6. Common Parameter Patterns

Income Limits (as FPL multiplier)

# income_limit/rate.yaml
description: State uses this multiplier of the federal poverty guideline for program income limits.
values:
  2024-01-01: 1.85  # 185% FPL

metadata:
  unit: /1
  period: year
  label: State PROGRAM income limit multiplier

Benefit Amounts

# payment_standard/amount.yaml
description: State provides this amount as the monthly program benefit.
values:
  2024-01-01: 500

metadata:
  unit: currency-USD
  period: month
  label: State PROGRAM payment standard amount

Age Thresholds

# age_threshold/minor_child.yaml
description: State defines minor children as under this age for program eligibility.
values:
  2024-01-01: 18

metadata:
  unit: year
  period: eternity
  label: State PROGRAM minor child age threshold

Disregard Percentages

# income/disregard/percentage.yaml
description: State excludes this share of earned income from program calculations.
values:
  2024-01-01: 0.67  # 67%

metadata:
  unit: /1
  period: eternity
  label: State PROGRAM earned income disregard percentage

---

7. Validation Checklist

Before creating parameters:

• Studied reference implementations (DC, IL, TX)
• All four metadata fields present
• Description is one complete sentence
• Values use underscore separators
• Trailing zeros removed from decimals
• References include subsections and page numbers
• Label follows naming pattern
• Effective date matches source document

---

8. Common Mistakes to Avoid

Missing Metadata

❌ WRONG - Missing required fields:
metadata:
  unit: currency-USD
  label: Benefit amount
  # Missing: period, reference

Generic References

❌ WRONG:
reference:
  - title: State TANF Manual
    href: https://state.gov/tanf

✅ CORRECT:
reference:
  - title: State TANF Manual Section 5.2, page 15
    href: https://state.gov/tanf-manual.pdf#page=15

Arbitrary Dates

❌ WRONG:
values:
  2000-01-01: 500  # Lazy default

✅ CORRECT:
values:
  2023-07-01: 500  # From source: "effective July 1, 2023"

---

Real-World Examples from Production Code

CRITICAL: Study actual parameter files, not just examples!

Before writing ANY parameter:

1. Open and READ 3+ similar parameter files from TX/IL/DC
2. COPY their exact description pattern
3. Replace state name and specific details only

Payment Standards

# Texas (actual production)
description: Texas provides this amount as the payment standard under the Temporary Assistance for Needy Families program.

# Pennsylvania (actual production)
description: Pennsylvania limits TANF benefits to households with resources at or below this amount.

Income Limits

# Indiana (should be)
description: Indiana limits gross income to this amount under the Temporary Assistance for Needy Families program.

# Texas (actual production)
description: Texas limits countable resources to this amount under the Temporary Assistance for Needy Families program.

Disregards

# Indiana (should be)
description: Indiana excludes this share of earnings from countable income under the Temporary Assistance for Needy Families program.

# Texas (actual production)
description: Texas deducts this standard work expense amount from gross earned income for Temporary Assistance for Needy Families program calculations.

Pattern Analysis

• ALWAYS spell out full program name
• Use "under the [Program] program" or "for [Program] program calculations"
• One simple verb (limits, provides, excludes, deducts)
• One "this X" placeholder
• NO extra explanation ("based on X", "This is Y")

Common Description Mistakes to AVOID

❌ WRONG - Using acronyms:

description: Indiana sets this gross income limit for TANF eligibility by household size.
# Problems: "TANF" not spelled out, unnecessary "by household size"

✅ CORRECT:

description: Indiana limits gross income to this amount under the Temporary Assistance for Needy Families program.

❌ WRONG - Adding explanatory text:

description: Indiana provides this payment standard amount based on household size.
# Problem: "based on household size" is unnecessary (evident from breakdown)

✅ CORRECT:

description: Indiana provides this amount as the payment standard under the Temporary Assistance for Needy Families program.

❌ WRONG - Missing program context:

description: Indiana sets the gross income limit.
# Problem: No program name, no "this amount"

✅ CORRECT:

description: Indiana limits gross income to this amount under the Temporary Assistance for Needy Families program.

Authoritative Source Requirements

ONLY use official government sources:

• ✅ State codes and administrative regulations
• ✅ Official state agency websites (.gov domains)
• ✅ Federal regulations (CFR, USC)
• ✅ State plans and official manuals (.gov PDFs)

NEVER use:

• ❌ Third-party guides (singlemotherguide.com, benefits.gov descriptions)
• ❌ Wikipedia
• ❌ Nonprofit summaries (unless no official source exists)
• ❌ News articles

---

For Agents

When creating parameters:

1. READ ACTUAL FILES - Study TX/IL/DC parameter files, not just skill examples
2. Include ALL metadata fields - missing any causes errors
3. Use exact effective dates from sources
4. Follow naming conventions (amount/rate/threshold)
5. Write simple descriptions with "this" placeholders and full program names
6. Include ONLY official government references with subsections and pages
7. Format values properly (underscores, no trailing zeros)