Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add agents/policyengine/policyengine-claude/parameter-locatorgit clone --depth 1 https://github.com/PolicyEngine/policyengine-claudeWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00053 | $0.04756 |
| Opus 5 | $0.00026 | $0.02378 |
| Sonnet 5 | $0.00011 | $0.00951 |
| Haiku 4.5 | $0.00005 | $0.00476 |
Grade A, and why
parameter-locator scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -sS https://api.policyengine.org/us/metadata | jq -r '.result.parameters | keys[]' | grep -c '^gov.states.ri.tax.income.credits.ctc' How it starts
The opening of the file, as written. The whole thing — 306 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Parameter Locator
Maps a reform provision (one mechanical change) to the PolicyEngine-US/UK/Canada parameter path that controls it. Returns:
- The YAML path
- Current value(s)
- The reform-dict snippet to flip it
- Confidence + adjacent parameters to consider
This is the Stage 2 (parametric classification) workhorse. If no parameter exists, this agent says so — the reform is then classified as structural (needs new variable logic) or not-possible by the reform-classifier.
Inputs
provisionfrompolicy-text-researcher(mechanical change, baseline → reform values)jurisdiction(e.g.,{country: us, state: RI}or{country: us}for federal)effective_date(when the change takes effect)
Process
Step 1: Load the relevant country-model knowledge
Invoke the appropriate Skill:
- US →
policyengine-usskill (federal + state) - UK →
policyengine-ukskill - Canada →
policyengine-canadaskill
Step 2: Identify the candidate parameter family
Common federal US patterns:
| Program | Path family |
|---|---|
| EITC | gov.irs.credits.eitc.{max, phase_in_rate, phase_out, eligibility} |
| CTC | gov.irs.credits.ctc.{amount, refundable, phase_out} |
| SALT cap | gov.irs.deductions.itemized.salt_and_real_estate.cap |
| Standard deduction | gov.irs.deductions.standard.amount |
| Tax brackets | gov.irs.income.bracket.rates / .thresholds |
Common state patterns:
| Program | Path family |
|---|---|
| State income tax rate (flat) | gov.states.{state}.tax.income.rate |
| State income tax brackets (graduated) | gov.states.{state}.tax.income.rates.brackets[N].{rate, threshold} |
| Per-filing-status brackets (GA-style) | gov.states.{state}.tax.income.main.{filing}.brackets[N].{rate, threshold} |
| State EITC | gov.states.{state}.tax.income.credits.earned_income.{match, rate} |
| State CTC | gov.states.{state}.tax.income.credits.ctc.{amount, age_limit, phase_out} |
| State CDCC | gov.states.{state}.tax.income.credits.cdcc.{match, rate} |
| State standard deduction | gov.states.{state}.tax.income.deductions.standard.{amount} |
| State personal exemption | gov.states.{state}.tax.income.exemptions.personal.{amount} |
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 306 lines · 53 tokens per session scan A 5871b7fbfb43
parameter-locator is an agent published in the GitHub repository PolicyEngine/policyengine-claude (31 stars, last pushed 8d ago), licensed MIT. It adds 53 tokens to every session and 4,756 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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