Borrowing it
Nothing to install: this file belongs to phase-rs/phase. 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/phase-rs/phase/main/.claude/skills/add-replacement-effect/SKILL.mdgit clone --depth 1 https://github.com/phase-rs/phaseWrote 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/phase-rs/phase/add-replacement-effect)<a href="https://agentmods.dev/skills/phase-rs/phase/add-replacement-effect"><img src="https://agentmods.dev/badge/skills/phase-rs/phase/add-replacement-effect/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/phase-rs/phase/add-replacement-effect"><img src="https://agentmods.dev/badge/skills/phase-rs/phase/add-replacement-effect.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 2 findings, 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 Rogue Agent · line 255 Skill modifies its own code, configuration, or behavior at runtime. Self-modification enables an agent to escalate privileges, disable safety constraints, or install persistent backdoors.Fix: Prevent the skill from modifying its own code, SKILL.md, or configuration files. Treat skill files as read-only at runtime.
- high Rogue Agent · line 278 Skill modifies its own code, configuration, or behavior at runtime. Self-modification enables an agent to escalate privileges, disable safety constraints, or install persistent backdoors.Fix: Prevent the skill from modifying its own code, SKILL.md, or configuration files. Treat skill files as read-only at runtime.
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 | $0.00058 | $0.04276 |
| Opus 5.5 | $0.00023 | $0.01710 |
| Sonnet 5.5 | $0.00012 | $0.00855 |
| Haiku 4.5 | $0.00006 | $0.00428 |
Grade A, and why
add-replacement-effect 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 2mo 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 — 280 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Adding a Replacement Effect
Replacement effects modify or prevent game events before they happen (MTG Rule 614.1). They are not triggered abilities — they don't use the stack. This skill covers wiring a new replacement through the pipeline: definition → parser → registry → handler → engine.
Before you start: Trace how shock lands work end-to-end. They're the most complete example: parse_shock_land() in oracle_replacement.rs → ReplacementDefinition with Optional mode → replacement pipeline → handle_replacement_choice() in engine_replacement.rs delivers the accept/decline effect inline → apply_post_replacement_effect() handles any remaining copy-target follow-up.
CR Verification Rule: Every CR number in annotations MUST be verified by grepping
docs/MagicCompRules.txtbefore writing. Do NOT rely on memory — 701.x and 702.x numbers are arbitrary sequential assignments that LLMs consistently hallucinate. Rungrep -n "^614.1" docs/MagicCompRules.txt(etc.) for every number. If you cannot find it, do not write the annotation.
MTG Rules Reference
| Rule | What it governs | Engine implication |
|---|---|---|
| 614.1 | Replacement effects modify events, don't use the stack | Handled in replacement.rs pipeline, not effects/ |
| 614.12 | Self-replacement effects apply even when the card isn't on the battlefield yet | find_applicable_replacements() scans the entering object in addition to battlefield |
| 614.1c + 614.12a | "As [permanent] enters" effects are replacement effects; a required choice is made before the permanent enters | Must resolve before zone change completes — see Interactive Replacements below |
| 616.1 | Multiple replacements on same event: affected player/controller chooses order | pipeline_loop() returns NeedsChoice when multiple candidates exist |
| 614.6 | A replacement can only apply once to a given event | applied: HashSet<ReplacementId> on ProposedEvent tracks this |
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.
- 2mo ago First seen · 280 lines · 58 tokens per session scan A 1129c69cb5eb
add-replacement-effect is a skill published in the GitHub repository phase-rs/phase (312 stars, last pushed today), licensed Apache-2.0. It adds 58 tokens to every session and 4,276 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.
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