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 JuanMarchetto/agent-skills --skill migration-validatorgit clone --depth 1 https://github.com/JuanMarchetto/agent-skillsWrote 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/juanmarchetto/agent-skills/migration-validator)<a href="https://agentmods.dev/skills/juanmarchetto/agent-skills/migration-validator"><img src="https://agentmods.dev/badge/skills/juanmarchetto/agent-skills/migration-validator/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/juanmarchetto/agent-skills/migration-validator"><img src="https://agentmods.dev/badge/skills/juanmarchetto/agent-skills/migration-validator.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 | $0.00051 | $0.01183 |
| Opus 5.5 | $0.00020 | $0.00473 |
| Sonnet 5.5 | $0.00010 | $0.00237 |
| Haiku 4.5 | $0.00005 | $0.00118 |
Grade A, and why
migration-validator scanned grade A with 0 findings 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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 88 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Migration Validation Checklist
Compilation Check
- Rust code compiles with
rustc --edition 2024 - No errors, only warnings acceptable if minor
- Clippy passes with 0 warnings (
cargo clippy)
Safety Check
- Count
unsafeblocks (target: 0 for easy/medium, minimize for hard) - Every
unsafeblock has a// SAFETY:comment - No raw pointer dereferences without bounds checking
- No transmute unless absolutely necessary
- No
unwrap()on user-controlled data
Semantic Equivalence
- Same function signature (equivalent types)
- Same behavior for all valid inputs
- Same error conditions / edge cases
- Overflow behavior matches (wrapping vs. checked)
- Printf format matches exactly (especially
%g→ custom format_g()) - Bool/int distinction preserved (C
int0/1 ≠ Rustbool)
Differential Testing
- Compile C with
cc -std=gnu11 -lm - Compile Rust with
rustc --edition 2024 - Run both with identical test inputs
- Compare outputs byte-by-byte (not just "looks similar")
- Test edge cases: empty input, max values, null/None, negative numbers
- Float tolerance: exact match preferred, tolerance only for known precision differences
Idiomatic Score
Enhanced formula with positive AND negative signals:
- Base: 100
- Negative:
- (unsafe_blocks * 10) - (clippy_warnings * 2) - (unwrap_count * 3) - (as_casts * 1) - Positive:
+ min(10, result_count * 2) + min(5, option_count) + min(5, iter_usage) - Ranges: 90-100 Excellent, 70-89 Good, 60-69 Acceptable, <60 Needs repair
Quality Floor (P0)
- Track baseline unsafe count from initial translation
- NEVER allow repair to increase unsafe above baseline
- If repair adds unsafe → reject that iteration, try again
- This prevents the "oscillation" problem where repair trades quality for compilation
Best-Version Tracking (P1)
- Keep the version with highest score throughout repair loop
- If nothing passes validation, use best version as fallback (not raw c2rust)
- Prefer: compiling version > high-score non-compiling > c2rust fallback
What ships with it
3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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 · 88 lines · 51 tokens per session scan A 78fd3c84c7b0
migration-validator is a skill published in the GitHub repository JuanMarchetto/agent-skills (5 stars, last pushed 7mo ago), licensed MIT. It adds 51 tokens to every session and 1,183 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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