# Azure Cost Analysis

> >

- **Type:** Skill
- **Install:** `agentstack add skill-mozilla-platform-ops-agent-skills-azure-cost-analysis`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [mozilla-platform-ops](https://agentstack.voostack.com/s/mozilla-platform-ops)
- **Installs:** 0
- **Category:** [Cloud & Infrastructure](https://agentstack.voostack.com/c/cloud-infrastructure)
- **Latest version:** 0.1.0
- **License:** MPL-2.0
- **Upstream author:** [mozilla-platform-ops](https://github.com/mozilla-platform-ops)
- **Source:** https://github.com/mozilla-platform-ops/agent-skills/tree/main/skills/azure-cost-analysis
- **Website:** https://agentskills.io/home

## Install

```sh
agentstack add skill-mozilla-platform-ops-agent-skills-azure-cost-analysis
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Azure Cost Analysis

Diagnostic toolkit for FXCI Azure CI cost investigations. Covers all 3 CI subscriptions and multiple cost dimensions (pool, SKU, region, service). Designed for both routine cost trend analysis and deep diagnostic investigations.

## Knowledge References

**Read first:**
@references/README.md
@references/user-inputs.md
@references/methodology.md

**Multi-dimensional and multi-subscription:**
@references/cost-dimensions.md
@references/multi-subscription.md

**API and task correlation:**
@references/cost-management-api.md
@references/taskcluster-task-counting.md

**For deep diagnostics:**
@references/fxci-config-lookup.md
@references/taskcluster-service-changes.md
@references/azure-spot-pricing.md
@references/spot-evictions.md

**Standalone SQL queries** (copy-paste-ready, one file per query):
- `queries/azure-task-counts.sql`
- `queries/spot-evictions.sql`
- `queries/retry-rate.sql`
- `queries/schema-sample.sql`

## Prerequisites

- Azure CLI (`az`) authenticated, with read access to the 3 CI subscriptions
- Python 3.10+
- `curl` (for Taskcluster API queries)
- Redash access (for `taskclusteretl.derived_task_summary` queries when correlating cost with tasks)

## Quick Start

### Routine: monthly cost trend
```bash
# Monthly costs by worker-pool-id, FXCI Azure DevTest
uv run scripts/query_costs.py --start 2026-01-01 --end 2026-03-31 --granularity monthly

# Compare two periods side by side
uv run scripts/query_costs.py --start 2026-01-01 --end 2026-03-31 --granularity monthly --compare-months

# Different subscription
uv run scripts/query_costs.py --start 2026-03-01 --end 2026-03-31 --subscription a30e97ab-734a-4f3b-a0e4-c51c0bff0701
```

### Diagnostic: investigating a cost increase

1. **Read methodology.md first** — picks daily-cost vs cost/task as your primary signal
2. **Run `query_costs.py` per subscription** for the period of interest, monthly + daily
3. **Check TC Engineering DevTest** as a control — if it didn't grow, rule out general Azure pricing event
4. **Group by Meter** in the Azure Portal Cost Analysis to see SKU-level breakdown
5. **Group by Resource location** if you suspect regional spot pricing changes — pair with `azure-spot-pricing.md` for the Retail Prices API
6. **Pull `derived_task_summary`** task data from Redash for the same window — see `taskcluster-task-counting.md` BigQuery section
7. **Verify pool config** via `fxci-config-lookup.md` — SKU, regions, maxCapacity, initialWeight haven't changed
8. **Check git history** of `worker-pools.yml` for cost-relevant changes during the window
9. **Check TC services repo** for cost-relevant changes — `taskcluster-service-changes.md`. Bugs in worker-manager/worker-scanner can drive cost in ways fxci-config can't explain.
10. **Check the TC issues tracker** for any bug reports filed around the cost-anomaly window — engineering may have observed symptoms before you did
11. **If pattern is broad cost/task increase across regions/pools** — investigate spot eviction (`spot-evictions.md`)
12. **If queue starvation observed alongside available capacity** — likely a TC service-level state issue; cross-check `taskcluster-service-changes.md`

### Comparing task counts for a specific push (chunk count investigations)
```bash
uv run scripts/count_push_tasks.py --date 2026.03.30
```

## Usage

### query_costs.py

Queries the Azure Cost Management REST API for actual costs grouped by `worker-pool-id`.

| Flag | Description |
|------|-------------|
| `--start` | Start date (YYYY-MM-DD), required |
| `--end` | End date (YYYY-MM-DD), required |
| `--granularity` | `monthly` or `daily` (default: `monthly`) |
| `--compare-months` | Show month-over-month deltas and identify top movers |
| `--top` | Number of top pools to display (default: 25) |
| `--output`, `-o` | Save raw API response as JSON |
| `--subscription` | Override subscription ID (default: FXCI Azure DevTest). Use Trusted FXCI: `a30e97ab-734a-4f3b-a0e4-c51c0bff0701`, TC Engineering: `8a205152-b25a-417f-a676-80465535a6c9` |

### count_push_tasks.py

Counts tasks per worker pool and test suite in a mozilla-central push task group. Use this for drilling into a single push (e.g. chunk count investigations). For batch analysis across many pushes/days, use the BigQuery approach in `taskcluster-task-counting.md`.

| Flag | Description |
|------|-------------|
| `--date` | Push date in TC index format: `YYYY.MM.DD` |
| `--push-index` | Which push on that date to analyze (default: 0 = first) |
| `--pool-filter` | Only show tasks matching this pool substring |

## Example Prompts

| Prompt | Action |
|--------|--------|
| "Why did Azure costs go up this month?" | Read `methodology.md`. Run `query_costs.py --compare-months` per subscription. Check TC Engineering as control. Group by Meter to identify SKU drivers. |
| "Show me daily costs for March" | `query_costs.py --start 2026-03-01 --end 2026-03-31 --granularity daily` |
| "Did per-task billing rate change?" | Compute volume-weighted cost/task by week using F8s v2 cost ÷ F8s v2 pool tasks. Read `methodology.md` for the cost/task amortization caveat. |
| "Which worker pools are most expensive?" | `query_costs.py` for the period, sorted by total spend. |
| "Are there new worker pools driving cost?" | `query_costs.py --compare-months`, look at the "new pools" section. |
| "Did test task volume increase?" | Pull `taskclusteretl.derived_task_summary` task counts via Redash for the period. See `taskcluster-task-counting.md`. |
| "Did spot prices change in our regions?" | Query Azure Retail Prices API for current SKU prices and effective dates. See `azure-spot-pricing.md`. |
| "Are spot evictions causing the cost rise?" | Pull eviction events from Azure Activity Log + worker-manager preemption events. See `spot-evictions.md`. |
| "Which test suites are running more on win11-64-24h2?" | `count_push_tasks.py --pool-filter win11-64-24h2` for two dates, compare suite counts. |
| "Did the VM SKU for this pool change?" | Check `worker-pools.yml` directly + git log via GitHub API. See `fxci-config-lookup.md`. |
| "Is the cost increase Azure-wide or CI-specific?" | Compare cost growth in TC Engineering DevTest vs CI subs. If TC Engineering is flat, it's CI-specific. |

## Workflow: Monthly Cost Review

1. **Query monthly costs** for the period of interest with `--compare-months`, all 3 subscriptions
2. **Identify top movers** — pools with the largest absolute increase
3. **Check for new pools** — pools that didn't exist in the prior period
4. **Compute cost/task** for stable-volume pools to detect rate vs volume changes
5. **Correlate with task volume** — use `count_push_tasks.py` for spot checks, BigQuery for batch
6. **Drill into test suites** — if a pool's cost grew, check which test suites gained the most tasks
7. **Save report** to `~/moz_artifacts/` with findings

## Workflow: Diagnostic Investigation

For deeper cost investigations (cost rising more than volume can explain):

1. Establish a clean baseline (a normal pre-anomaly month — see `methodology.md`)
2. Compute volume-weighted daily cost/task; find the inflection date
3. Rule out, with evidence: general Azure pricing event (TC Engineering control), single-region spot spike, OS/SKU migration, regional traffic shifts, volume alone
4. Check **fxci-config** git history for changes in the inflection window
5. Check **taskcluster/taskcluster** git history for service-level changes (worker-manager, worker-scanner) in the window
6. Check the **taskcluster/taskcluster issues tracker** for bug reports filed around the window
7. Pull spot price effective dates from Retail Prices API
8. If pattern is broad cost/task increase across pools/regions: pull spot eviction telemetry from `fxci.task_runs`
9. If queue starvation observed alongside available capacity: investigate TC service state-tracking bugs
10. If structural changes (maxCapacity, initialWeight) candidate: design a rollback experiment

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [mozilla-platform-ops](https://github.com/mozilla-platform-ops)
- **Source:** [mozilla-platform-ops/agent-skills](https://github.com/mozilla-platform-ops/agent-skills)
- **License:** MPL-2.0
- **Homepage:** https://agentskills.io/home

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** yes
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-mozilla-platform-ops-agent-skills-azure-cost-analysis
- Seller: https://agentstack.voostack.com/s/mozilla-platform-ops
- Browse the marketplace: https://agentstack.voostack.com/browse

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