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 existential-birds/beagle --skill ffi-code-reviewgit clone --depth 1 https://github.com/existential-birds/beagleWrote 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/existential-birds/beagle/ffi-code-review)<a href="https://agentmods.dev/skills/existential-birds/beagle/ffi-code-review"><img src="https://agentmods.dev/badge/skills/existential-birds/beagle/ffi-code-review/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/existential-birds/beagle/ffi-code-review"><img src="https://agentmods.dev/badge/skills/existential-birds/beagle/ffi-code-review.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 | $0.00052 | $0.02422 |
| Opus 5.5 | $0.00021 | $0.00969 |
| Sonnet 5.5 | $0.00010 | $0.00484 |
| Haiku 4.5 | $0.00005 | $0.00242 |
Grade A, and why
ffi-code-review 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 — 158 lines — stays where its author put it; the contents beside it link to each section on GitHub.
FFI Code Review
Review Workflow
- Check Cargo.toml -- Note Rust edition (2024 has breaking changes to extern blocks and unsafe attributes),
build-dependencies(bindgen, cc, pkg-config),crate-type(cdylib,staticlib), andlinkskey - Check build.rs -- Verify link directives (
cargo:rustc-link-lib,cargo:rustc-link-search), bindgen configuration, and C source compilation - Check extern blocks -- Verify calling conventions, symbol declarations, and safety annotations
- Check type layout -- Every type crossing FFI must be
#[repr(C)]or a primitive FFI type - Check string and pointer handling -- CStr/CString usage, null checks, ownership transfers
- Check callbacks --
extern "C" fnpointers, panic safety across FFI boundary - Gates -- Complete Gates below before reporting; do not skip ahead on “internal verification”
Gates
Complete in order. Do not emit findings until Gate 4 passes for each issue.
Gate 1 — Crate context (on disk)
PASS when: You opened the reviewed crate’s Cargo.toml (workspace member path if applicable) and recorded edition =, plus any of links, crate-type, or build-dependencies that matter for this FFI.
Blocks rationalization: Edition-specific findings (unsafe extern "C" {}, #[unsafe(no_mangle)], etc.) require this — if edition is not 2024, do not flag 2024-only requirements.
Gate 2 — Linkage and binding sources
PASS when: If the crate links native code or uses bindgen/pkg-config, you opened build.rs (or the checked-in bindings entry point). If there is no build.rs, you stated that bindings are hand-written and reviewed those extern / include! sites.
Artifact: At least one path you opened (e.g. build.rs, src/ffi.rs, or OUT_DIR bindings via include!).
Gate 3 — Code evidence
PASS when: Every planned finding has a target [FILE:LINE] from a full function/block you read, not only diff hunks or partial snippets.
What ships with it
2 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 · 158 lines · 52 tokens per session scan A 5cfa0bdafb76
ffi-code-review is a skill published in the GitHub repository existential-birds/beagle (82 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 52 tokens to every session and 2,422 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 2026-09-16.
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