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 justanesta/claude-code-resources --skill developing-packages-rgit clone --depth 1 https://github.com/justanesta/claude-code-resourcesWrote 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/justanesta/claude-code-resources/developing-packages-r)<a href="https://agentmods.dev/skills/justanesta/claude-code-resources/developing-packages-r"><img src="https://agentmods.dev/badge/skills/justanesta/claude-code-resources/developing-packages-r/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/justanesta/claude-code-resources/developing-packages-r"><img src="https://agentmods.dev/badge/skills/justanesta/claude-code-resources/developing-packages-r.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 | $0.00076 | $0.00805 |
| Opus 5.5 | $0.00030 | $0.00322 |
| Sonnet 5.5 | $0.00015 | $0.00161 |
| Haiku 4.5 | $0.00008 | $0.00081 |
Grade A, and why
developing-packages-r 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 — 117 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Developing Packages R
This skill covers building robust R packages with modern patterns and best practices.
Dependency Strategy
When to Add Dependencies vs Base R
Add dependency when:
- Significant functionality gain
- Maintenance burden reduction
- User experience improvement
- Complex implementation (regex, dates, web)
Use base R when:
- Simple utility functions
- Package will be widely used (minimize deps)
- Dependency is large for small benefit
- Base R solution is straightforward
See dependency-decisions.md for example decisions.
Tidyverse Dependency Guidelines
| Category | Packages | Guidance |
|---|---|---|
| Core (usually worth it) | dplyr, purrr, stringr, tidyr | Complex manipulation, functional programming |
| Specialized (evaluate carefully) | lubridate, forcats, readr, ggplot2 | Only if heavy usage |
| Heavy (use sparingly) | tidyverse, shiny | Meta-package or interactive apps only |
API Design Patterns
Modern Tidyverse API
See api-design.md for:
- Use
.byfor per-operation grouping - Use
{{ }}for user-provided columns - Use
...for flexible arguments - Return consistent types (tibbles, not data.frames)
Input Validation Strategy
Validation level depends on function type:
| Function Type | Validation Level |
|---|---|
| User-facing | Comprehensive - check all inputs |
| Internal | Minimal - assume valid, check invariants |
| vctrs-based | Type-stable - automatic checking |
See validation-patterns.md for examples.
Error Handling Patterns
Good error messages are:
- Specific - say what went wrong
- Actionable - say how to fix it
- Traceable - include function context
See error-handling.md for:
- cli package for user-friendly messages
- rlang for developer tools
- Including function name in errors
What ships with it
6 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.
- 2mo ago First seen · 117 lines · 76 tokens per session scan A d58a98f52d17
developing-packages-r is a skill published in the GitHub repository justanesta/claude-code-resources (2 stars, last pushed 6mo ago), licensed MIT. It adds 76 tokens to every session and 805 once invoked, about $0.0003 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 2026-08-31.
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