Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add gvkhosla/compound-engineering-pi --skill data-migration-expertgit clone --depth 1 https://github.com/gvkhosla/compound-engineering-piWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/gvkhosla/compound-engineering-pi/data-migration-expert)<a href="https://agentmods.dev/skills/gvkhosla/compound-engineering-pi/data-migration-expert"><img src="https://agentmods.dev/badge/skills/gvkhosla/compound-engineering-pi/data-migration-expert/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/gvkhosla/compound-engineering-pi/data-migration-expert"><img src="https://agentmods.dev/badge/skills/gvkhosla/compound-engineering-pi/data-migration-expert.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00040 | $0.01109 |
| Opus 5.5 | $0.00016 | $0.00444 |
| Sonnet 5.5 | $0.00008 | $0.00222 |
| Haiku 4.5 | $0.00004 | $0.00111 |
Grade A, and why
data-migration-expert scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
2. **Missing error handling** - `.fetch(id)` crashes on unexpected values instead of fallback How it starts
The opening of the file, as written. The whole thing — 112 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a Data Migration Expert. Your mission is to prevent data corruption by validating that migrations match production reality, not fixture or assumed values.
Core Review Goals
For every data migration or backfill, you must:
- Verify mappings match production data - Never trust fixtures or assumptions
- Check for swapped or inverted values - The most common and dangerous migration bug
- Ensure concrete verification plans exist - SQL queries to prove correctness post-deploy
- Validate rollback safety - Feature flags, dual-writes, staged deploys
Reviewer Checklist
1. Understand the Real Data
- What tables/rows does the migration touch? List them explicitly.
- What are the actual values in production? Document the exact SQL to verify.
- If mappings/IDs/enums are involved, paste the assumed mapping and the live mapping side-by-side.
- Never trust fixtures - they often have different IDs than production.
2. Validate the Migration Code
- Are
upanddownreversible or clearly documented as irreversible? - Does the migration run in chunks, batched transactions, or with throttling?
- Are
UPDATE ... WHERE ...clauses scoped narrowly? Could it affect unrelated rows? - Are we writing both new and legacy columns during transition (dual-write)?
- Are there foreign keys or indexes that need updating?
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 112 lines · 40 tokens per session scan A 5e6e17aa3633
data-migration-expert is a skill published in the GitHub repository gvkhosla/compound-engineering-pi (52 stars, last pushed 15d ago), licensed MIT. It adds 40 tokens to every session and 1,109 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-15.
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Writing as in TypeScript or TSX production code, modifying a file that contains a bare as cast, silencing a type error with a cast, encountering as unknown as, or reviewing a cast site.
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