rtk is a command-line proxy that filters and compresses output from development commands before it reaches an LLM's context. It is used with coding agents to reduce the tokens consumed by commands such as Git operations. The catalogue includes skills, commands, agents, and instructions for using rtk in agent workflows.
Borrowing it
Nothing to install: this file belongs to rtk-ai/rtk. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/rtk-ai/rtk/develop/.claude/skills/rtk-tdd/SKILL.mdgit clone --depth 1 https://github.com/rtk-ai/rtkWrote 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/rtk-ai/rtk/rtk-tdd)<a href="https://agentmods.dev/skills/rtk-ai/rtk/rtk-tdd"><img src="https://agentmods.dev/badge/skills/rtk-ai/rtk/rtk-tdd/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/rtk-ai/rtk/rtk-tdd"><img src="https://agentmods.dev/badge/skills/rtk-ai/rtk/rtk-tdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Privilege Escalation · line 57 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
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 | $0.00061 | $0.00783 |
| Opus 5.5 | $0.00024 | $0.00313 |
| Sonnet 5.5 | $0.00012 | $0.00157 |
| Haiku 4.5 | $0.00006 | $0.00078 |
Grade A, and why
rtk-tdd 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 — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Rust TDD Workflow
Three Laws of TDD
- Do NOT write production code without a failing test
- Write only enough test to fail (including compilation failure)
- Write only enough production code to pass the failing test
Cycle: RED (test fails) -> GREEN (minimum to pass) -> REFACTOR (cleanup, cargo test)
Red-Green-Refactor Steps
1. Write test in #[cfg(test)] mod tests of the SAME file
2. cargo test MODULE::tests::test_name -- must FAIL (red)
3. Implement the minimum in the function
4. cargo test MODULE::tests::test_name -- must PASS (green)
5. Refactor if needed, re-run cargo test (still green)
6. cargo fmt && cargo clippy --all-targets && cargo test (final gate)
Never skip step 2. If the test passes immediately, it tests nothing.
Idiomatic Rust Test Patterns
| Pattern | Usage | When |
|---|---|---|
| Arrange-Act-Assert | Base structure for every test | Always |
assert_eq! / assert! |
Direct comparison / booleans | Deterministic values |
assert!(result.is_err()) |
Error path testing | Invalid inputs |
Result<()> return type |
Tests with ? operator |
Fallible functions |
#[should_panic] |
Expected panic | Invariants, preconditions |
tempfile::NamedTempFile |
File/I/O tests | Filesystem-dependent code |
Patterns by Code Type
| Code Type | Test Pattern | Example |
|---|---|---|
| Pure function (str -> str) | Input literal -> assert output | assert_eq!(truncate("hello", 3), "...") |
| Parsing/filtering | Raw string -> filter -> contains/not-contains | assert!(filter(raw).contains("expected")) |
| Validation/security | Boundary inputs -> assert bool | assert!(!is_valid("../etc/passwd")) |
| Error handling | Bad input -> is_err() |
assert!(parse("garbage").is_err()) |
| Struct/enum roundtrip | Construct -> serialize -> deserialize -> eq | assert_eq!(from_str(to_str(x)), x) |
Naming Convention
test_{function}_{scenario}
test_{function}_{input_type}
What ships with it
1 file 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 · 86 lines · 61 tokens per session scan A 82b156358322
rtk-tdd is a skill published in the GitHub repository rtk-ai/rtk (84,655 stars, last pushed yesterday), licensed Apache-2.0. It adds 61 tokens to every session and 783 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 2026-08-30.
Other skills, from other repositories
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plan-pipeline-execute
Execute a validated plan: worktree isolation, TDD scaffolding, level-based parallel agents, quality gate with smoke test, PR creation and merge. Handles everything through to merged PR.
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python-testing
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atomic-tdd
Test-first discipline. Auto-triggers on "let's implement X", "add feature Y", "fix bug Z", "write a test for", "implement", "build out", and similar pre-code-change phrases. Iron rule: failing test exists before production code. Skip only for pure docs/config changes with an explicit "skipped because:" note. Explicit…
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Guide for Rust development including code style, testing, building, and quality checks using cargo tools. Apply when working with Rust code, Cargo.toml, or running cargo commands.