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 ALL findings using the Zero Hallucination Pricing System. Every finding must have a verifiable pricing_source. Findings without a pricing source or with fabricated prices are rejected (set to monthly_savings=0 with pricing_unknown=true).

Quick Start

# Validate with default $100 threshold (queries API only for >$100 findings)
python3 "${CLAUDE_PLUGIN_ROOT}/skills/validating-aws-pricing/scripts/validate_pricing.py" findings.json --profile your-profile

# Lower threshold to validate more findings
python3 "${CLAUDE_PLUGIN_ROOT}/skills/validating-aws-pricing/scripts/validate_pricing.py" findings.json --profile your-profile --threshold 50

# Works with any AWS auth method (SSO, access keys, IAM role)
python3 "${CLAUDE_PLUGIN_ROOT}/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. Preserves pricing that already carries a compliant pricing_source and calculation
2. Resolves from the verified us-east-1 table where an exact formula exists
3. Otherwise sets monthly_savings=0 with pricing_unknown=true — it NEVER estimates

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

savings = hourly_rate * 730  # Resource should be terminated

Unattached Storage (EC2-012, EBS-001)

Savings = Storage cost per month

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

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

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 (LOG-001)

Savings = Storage cost that can be avoided with retention policy

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.

Output

The script updates findings.json in place:

{
  "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)
- [ ] ANTI-HALLUCINATION CHECKS (run first):
  - [ ] Every finding has details.pricing_source (reject if missing)
  - [ ] Every finding with savings > 0 has details.calculation (reject if missing)
  - [ ] No findings have savings > 0 with pricing_source="pricing_unknown" (reject if found)
  - [ ] No idle findings count missing metrics as zero activity (reject if found)
  - [ ] Downsize targets are same-family-one-size-down or from Compute Optimizer (reject if not)
- [ ] For EACH finding:
  - [ ] Verify formula matches finding type
  - [ ] Check savings <= service spend (sanity check)
  - [ ] Query AWS Pricing API for ALL findings with pricing_source != "aws_pricing_api"
  - [ ] Check OS matches (Windows vs Linux) for EC2 findings
  - [ ] Check deployment option matches (Multi-AZ vs Single-AZ) for RDS findings
  - [ ] Check all EBS components (storage + IOPS + throughput) for EBS findings
  - [ ] Recalculate if errors found
  - [ ] Add calculation breakdown to details
- [ ] Flag any corrected findings with pricing_corrected: true
- [ ] Set any unfixable findings to monthly_savings=0 with pricing_unknown=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

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:

aws ce get-cost-and-usage --profile {profile} \
  --time-period Start={LAST_MONTH_START},End={LAST_MONTH_END} \
  --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:

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

CORRECT:

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

Even more correct (check what % is older than retention):

# 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:

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

Over-provisioned RDS

CORRECT:

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:

{
  "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
    }
  }
}