Maverick spend detection

# Maverick spend detection (off-policy purchases)

## Purpose
Identify spend made outside the approved supplier list (maverick spend). Measure the purchasing policy compliance rate and identify at-risk teams or categories.

**Limitation:** Spendesk does not natively store an "approved vs non-approved suppliers" list. This skill builds a proxy by distinguishing regular active suppliers from new one-shot suppliers.

## Instructions

### Step 1 — Build the proxy list of "established" suppliers
```
Call spendesk_analyze_spend with:
  - groupBy: supplier
  - Period: last 12 months

Build the proxy list:
  "Established" supplier = at least 3 transactions AND at least 2 different invoicing months
  "New" or "one-shot" supplier = 1-2 transactions over the period

Note: this criterion is an approximation. Ideally, the approved supplier list
would come from an ERP or an import file.
```

### Step 2 — Identify spend outside the proxy list
```
Call get_payables for the last 3 months.
For each payable:
  Check if the supplierId is in the "established" list
  If not → potential maverick spend

For the identified one-shot suppliers:
  Call get_supplier_by_id to retrieve the name and country.
  Note: even for a single supplier, the response can be large if its accountPayable is a shared consolidated account (see [[s22-fournisseurs-actifs-iban]]) — this is expected, not an error.
```

### Step 3 — Analyze maverick spend patterns
```
Group maverick spend by:
  - Cost center (which team buys off-list?)
  - Expense category (what type of purchase is involved?)
  - Amount (one-off purchase vs recurring commitment?)

Calculate:
  Total maverick spend: X€ (X% of total spend)
  Number of one-shot suppliers: X
  Cost centers with the most maverick spend
```

### Step 4 — Identify risks
```
Risk levels:
  🔴 HIGH: new supplier, amount > 5,000€, no associated PO
  🟡 MODERATE: new supplier, amount 1,000-5,000€ or recurrence
  🟢 LOW: one-off purchase < 1,000€ (may be acceptable)

For high risks:
  Did the requester have a justified need?
  Is there an equivalent approved supplier?
```

### Step 5 — Maverick spend report
```
Present:
1. Purchasing compliance rate:
   Spend with approved suppliers: X€ (X%)
   Maverick spend: X€ (X%)
   Target objective: < 10% (procurement best practice)

2. Top 5 one-shot suppliers by amount:
   Supplier | Amount | Nb transactions | Cost center | Category | Risk

3. Cost centers with the most maverick spend:
   Team | Maverick amount | % of their total spend

4. At-risk categories:
   Category | Maverick spend | Approved suppliers available?

5. Recommendations:
   - Onboard recurring one-shot suppliers as approved
   - Train the offending teams
   - Implement preventive controls
```

## Points of attention
- This skill produces a proxy — not all "one-shot suppliers" are necessarily maverick spend (some one-off purchases are legitimate)
- The optimal maverick spend rate depends on the sector and procurement maturity (target < 10%)
- This skill is complementary to the tail spend skill (s57) — maverick spend is a subset of tail spend

## Example prompts
- "What is our maverick spend rate this quarter?"
- "Which teams buy the most off the approved supplier list?"
- "Identify off-policy purchases from the last 3 months"