Validating Aws Pricing

---
name: validating-aws-pricing
description: MANDATORY validation of AWS cost findings. Cross-checks savings estimates against actual billing data and correct pricing formulas. Catches errors like confusing storage vs ingestion costs. Run BEFORE generating any report.
allowed-tools:
  - Read
  - Write
  - Bash
  - Grep
  - mcp__awslabs-aws-api__call_aws
---

# Validating AWS Pricing

**MANDATORY** validation step that catches pricing errors before they reach the user.

## Why This Matters

Common errors this skill catches:
- CloudWatch Logs: Confusing $0.50/GB ingestion with $0.03/GB storage
- Savings exceeding actual service spend (impossible)
- Wrong multipliers or formulas
- Missing cost components

## Purpose

This skill validates pricing for significant findings using live AWS Pricing API. Smaller findings use fallback estimates to avoid unnecessary API calls.

## Quick Start

```bash
# Validate with default $100 threshold (queries API only for >$100 findings)
python skills/validating-aws-pricing/scripts/validate_pricing.py findings.json --profile ctm

# Lower threshold to validate more findings
python skills/validating-aws-pricing/scripts/validate_pricing.py findings.json --profile ctm --threshold 50

# Works with any AWS auth method (SSO, access keys, IAM role)
python skills/validating-aws-pricing/scripts/validate_pricing.py findings.json  # uses default credentials
```

## What Gets Updated

For findings **above threshold** (default $100):
1. Queries real AWS Pricing API for EC2, RDS, EBS
2. Updates `monthly_savings` with validated value
3. Marks `api_validated: true` in metadata

For findings **below threshold**:
1. Uses fallback estimates (fast, no API calls)
2. Marks `api_validated: false` in metadata

All findings get `pricing_validated` metadata showing the source.

## Pricing Calculation by Finding Type

### Idle Resources (EC2-001, etc.)
Savings = Full monthly cost of the resource
```python
savings = hourly_rate * 730  # Resource should be terminated
```

### Unattached Storage (EC2-012, EBS-001)
Savings = Storage cost per month
```python
savings = size_gb * price_per_gb  # e.g., 100GB * $0.08 = $8.00
```

### Over-provisioned (RDS-002, LAMBDA-001)
Savings = Difference between current and recommended size
```python
current_cost = current_hourly * 730
recommended_cost = recommended_hourly * 730
savings = current_cost - recommended_cost
```

### No RI Coverage (RDS-005)
Savings = On-Demand cost - Reserved Instance cost
```python
on_demand_monthly = hourly_rate * 730
ri_monthly = ri_upfront / 12 + ri_hourly * 730
savings = on_demand_monthly - ri_monthly  # ~40-60% typically
```

### CloudWatch Logs (SEC-001)
Savings = Storage cost that can be avoided with retention policy
```python
savings = stored_gb * 0.03  # $0.03 per GB-month
```

## AWS Pricing Reference

Current pricing (us-east-1):

| Resource | Price | Unit | Monthly (730 hrs) |
|----------|-------|------|-------------------|
| t2.nano | $0.0058 | /hour | $4.23 |
| t3.nano | $0.0052 | /hour | $3.80 |
| gp3 storage | $0.08 | /GB-month | - |
| db.r5.xlarge | $0.50 | /hour | $365.00 |
| cache.t3.small (Valkey) | $0.0272 | /hour | $19.86 |
| CloudWatch Logs | $0.03 | /GB-month | - |

For complete pricing, see [PRICING_REFERENCE.md](PRICING_REFERENCE.md).

## Output

The script updates `findings.json` in place:

```json
{
  "check_id": "EC2-001",
  "monthly_savings": 4.23,
  "pricing_validated": {
    "source": "AWS Pricing API",
    "validated_at": "2026-01-19T10:00:00Z",
    "hourly_rate": 0.0058,
    "calculation": "0.0058 * 730 hours"
  }
}
```

## Workflow

1. Load `findings.json`
2. For each finding:
   - Identify resource type from `check_id` and `details`
   - Query AWS Pricing API (or use cached known prices)
   - Calculate correct savings based on finding category
   - Update `monthly_savings` field
   - Add `pricing_validated` metadata
3. Recalculate `total_monthly_savings` in metadata
4. Save updated `findings.json`

## Task Checklist

```
- [ ] Load findings.json
- [ ] Get actual billing from Cost Explorer (by service AND usage type)
- [ ] For EACH finding:
  - [ ] Verify formula matches finding type
  - [ ] Check savings <= service spend (sanity check)
  - [ ] Query AWS Pricing API if > $100
  - [ ] Recalculate if errors found
  - [ ] Add calculation breakdown to details
- [ ] Flag any corrected findings with pricing_corrected: true
- [ ] Recalculate total savings in metadata
- [ ] Save corrected findings.json
- [ ] Regenerate report with accurate prices
```

---

## CRITICAL: Sanity Check Rules

### Rule 1: Savings Cannot Exceed Service Spend

```python
assert finding.monthly_savings <= service_monthly_spend, \
    f"Finding {finding.check_id} claims ${finding.monthly_savings} but service only costs ${service_monthly_spend}"
```

**Example Failure:**
- Finding: CloudWatch Logs retention saves $594/mo
- Billing: CloudWatch total spend = $159/mo
- **INVALID** - immediately flag and recalculate

### Rule 2: Use Correct Cost Component

Many AWS services have MULTIPLE cost components:

| Service | Components | What Retention Affects |
|---------|------------|------------------------|
| **CloudWatch Logs** | Ingestion ($0.50/GB) + Storage ($0.03/GB) | Storage ONLY |
| **S3** | Storage + Requests + Transfer | Storage + old versions |
| **EBS** | Storage + IOPS + Throughput | Storage ONLY |
| **RDS** | Compute + Storage + I/O | Depends on finding |

### Rule 3: Verify With Usage Type Breakdown

For any finding > $100, get usage-type breakdown:

```bash
aws ce get-cost-and-usage --profile {profile} \
  --time-period Start=2025-12-01,End=2026-01-01 \
  --granularity MONTHLY \
  --metrics UnblendedCost \
  --filter '{"Dimensions": {"Key": "SERVICE", "Values": ["AmazonCloudWatch"]}}' \
  --group-by Type=DIMENSION,Key=USAGE_TYPE
```

This shows:
- `DataProcessing-Bytes`: Log ingestion ($0.50/GB)
- `TimedStorage-ByteHrs`: Log storage ($0.03/GB)

**Only storage can be reduced by retention policy!**

---

## Common Pricing Mistakes & Corrections

### CloudWatch Logs Retention

**WRONG:**
```python
savings = stored_gb * 0.50  # Using ingestion price!
# 221 GB * $0.50 = $110.50  # WRONG!
```

**CORRECT:**
```python
savings = stored_gb * 0.03  # Storage price
# 221 GB * $0.03 = $6.63    # CORRECT!
```

**Even more correct (check what % is older than retention):**
```python
# If setting 90-day retention, only logs older than 90 days are deleted
# Estimate 50% of stored data is older than 90 days
savings = stored_gb * 0.03 * 0.5
```

### Unattached EBS Volume

**CORRECT:**
```python
savings = size_gb * price_per_gb
# gp3: 100 GB * $0.08 = $8.00
# gp2: 100 GB * $0.10 = $10.00
```

### Over-provisioned RDS

**CORRECT:**
```python
current_cost = current_hourly * 730
recommended_cost = recommended_hourly * 730
savings = current_cost - recommended_cost

# db.r5.xlarge -> db.r5.large
# $0.50 * 730 - $0.25 * 730 = $365 - $182.50 = $182.50
```

---

## Validation Output Format

After validation, each finding should include:

```json
{
  "check_id": "LOG-001",
  "monthly_savings": 6.64,
  "pricing_validated": {
    "validated_at": "2026-01-19T12:00:00Z",
    "original_estimate": 594.34,
    "corrected": true,
    "correction_reason": "Used storage price ($0.03/GB) instead of ingestion price ($0.50/GB)",
    "calculation": "221.4 GB × $0.03/GB = $6.64",
    "sanity_check": {
      "service": "AmazonCloudWatch",
      "service_spend": 159.13,
      "finding_savings": 6.64,
      "passed": true
    }
  }
}
```