# Highest_Cost_Scenario_Identification

> Solve dabstep dataset questions that ask to identify the most expensive Merchant Category Code (MCC) or the most expensive Authorization Characteristics Indicator (ACI) for a given transaction. Use this skill when the question asks "what is the most expensive MCC for a transaction of X euros" or "what is the most expensive ACI for a credit/debit transaction of X euros on [CardScheme]".

- Skill: `zjunlp/highest-cost-scenario-identification-3` (Agent Skill)
- Install (CLI): `npx skillmds@latest add zjunlp/highest-cost-scenario-identification-3`
- Raw SKILL.md: https://api.skillmd.com/api/skills/zjunlp/highest-cost-scenario-identification-3/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: zjunlp (https://skillmd.com/u/zjunlp)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/zjunlp/highest-cost-scenario-identification-3

---


# Highest Cost Scenario Identification

This skill covers two question types in the dabstep dataset, both requiring fee calculation from `fees.json`.

## Fee Formula

```
fee = fixed_amount + rate * transaction_value / 10000
```

**Key data facts (verified from actual files):**
- `fees.json` has 1000 rules; `card_scheme` is never null
- `is_credit`: `True` = credit only, `False` = debit only, `null/None` = both credit and debit
- `aci` field: either `[]` (empty list, 112 rules) or a non-empty list of letters — never null
- `merchant_category_code` field: either `[]` (empty list, 127 rules) or a non-empty list of integers — never null
- ACI values in fee rules: A, B, C, D, E, F only (G does not appear in any fee rule)
- Card schemes: `GlobalCard`, `NexPay`, `SwiftCharge`, `TransactPlus`

**Empty list semantics for this question type**: An empty list `[]` for `aci` or `merchant_category_code` means the rule applies to ALL values of that field (same as null for scalar fields). However, for "most expensive ACI/MCC" questions, rules with `aci=[]` apply equally to every ACI and cannot differentiate which ACI costs more — **skip them**. Same logic for `merchant_category_code=[]` in MCC questions.

---

## Question Type 1: Most Expensive MCC

**Pattern**: "What is the most expensive MCC for a transaction of X euros, in general?"

**Algorithm**:
1. Load `fees.json`
2. For every rule, skip if `merchant_category_code` is empty (`[]`)
3. Compute `fee = fixed_amount + rate * X / 10000`
4. For each MCC in the rule's list, track the maximum fee seen across all rules
5. Return all MCCs (sorted ascending) that tie for the global maximum fee

**Critical**: No card_scheme or is_credit filter for "in general" MCC questions. Include ALL fee rules (regardless of card_scheme, is_credit, etc.) — only skip rules with empty `merchant_category_code`. Do NOT restrict to MCCs listed in `merchant_category_codes.csv`.

**Output format**: Comma-separated MCC integers, sorted ascending. Example: `3000, 3001, 7512`

```python
import json

with open('fees.json') as f:
    fees = json.load(f)

transaction_value = X  # from question
mcc_max_fees = {}

for rule in fees:
    mcc_list = rule['merchant_category_code']
    if not mcc_list:  # skip [] (applies to all, doesn't differentiate)
        continue
    fee = rule['fixed_amount'] + rule['rate'] * transaction_value / 10000
    for mcc in mcc_list:
        if mcc not in mcc_max_fees or fee > mcc_max_fees[mcc]:
            mcc_max_fees[mcc] = fee

max_fee = max(mcc_max_fees.values())
result = sorted([mcc for mcc, f in mcc_max_fees.items() if f == max_fee])
print(', '.join(str(m) for m in result))
```

---

## Question Type 2: Most Expensive ACI

**Pattern**: "For a [credit/debit] transaction of X euros on [CardScheme], what would be the most expensive ACI? In the case of a draw between multiple ACIs, return the ACI with the lowest alphabetical order."

**Algorithm**:
1. Load `fees.json`
2. Filter rules: `card_scheme == CardScheme`
3. Filter by transaction type:
   - Credit transaction: include rules where `is_credit` is `True` or `None`
   - Debit transaction: include rules where `is_credit` is `False` or `None`
4. Skip rules where `aci` list is empty (`[]`)
5. Compute `fee = fixed_amount + rate * X / 10000`
6. For each ACI in the rule's list, track the maximum fee seen
7. Return the ACI(s) with the highest fee; if tied, return the alphabetically lowest

> **CRITICAL — the answer is an ACI letter, NOT a fee amount.** The task instructions may show `<answer>0.23</answer>` as a generic format placeholder — that `0.23` is irrelevant to ACI questions. Your answer must be the ACI letter in a list: `['A']`, `['B']`, ..., `['F']`. Never return a numeric fee value.

**Output format**: A Python list containing one letter string. Example: `['E']`

```python
import json

with open('fees.json') as f:
    fees = json.load(f)

card_scheme = 'NexPay'      # from question
transaction_value = 1       # from question (in euros)
is_credit = True            # True for credit, False for debit

aci_max_fees = {}

for rule in fees:
    if rule['card_scheme'] != card_scheme:
        continue
    # None means applies to all (credit and debit); include for the target type
    if rule['is_credit'] is not None and rule['is_credit'] != is_credit:
        continue
    aci_list = rule['aci']
    if not aci_list:  # skip [] (applies to all, doesn't differentiate)
        continue
    fee = rule['fixed_amount'] + rule['rate'] * transaction_value / 10000
    for aci in aci_list:
        if aci not in aci_max_fees or fee > aci_max_fees[aci]:
            aci_max_fees[aci] = fee

max_fee = max(aci_max_fees.values())
winners = sorted([aci for aci, f in aci_max_fees.items() if f == max_fee])
answer = winners[0]  # alphabetically lowest in case of tie
print([answer])      # output as a list, e.g. ['E']
```

---

## Common Mistakes

1. **Returning the fee amount instead of the ACI letter**: The answer is always a letter (e.g., `['E']`), never a number like `0.23` or `0.1467`. The `0.23` in task format examples is just a generic placeholder unrelated to ACI answers.
2. **MCC filtering**: Never exclude an MCC just because it's absent from `merchant_category_codes.csv`. The fee rules are the sole source of truth for MCC questions.
3. **Empty lists `[]`**: Skip rules where `merchant_category_code` or `aci` is `[]` for these question types — they apply to all values equally and don't differentiate costs by MCC or ACI.
4. **is_credit for ACI questions**: Include rules with `is_credit=None` (applies to all transaction types), not only `is_credit=True` (for credit) or `False` (for debit).
5. **Tie-breaking for ACI**: When multiple ACIs share the maximum fee, return the alphabetically first one (e.g., `'A'` before `'B'`).
6. **MCC questions — no card_scheme filter**: For "in general" MCC questions, do NOT filter by card_scheme or is_credit. All fee rules contribute regardless of scheme.