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 agentmods add skills/nschneir/project64/c64-developmentnpx skills add nschneir/Project64 --skill c64-developmentgit clone --depth 1 https://github.com/nschneir/Project64Wrote 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/nschneir/project64/c64-development)<a href="https://agentmods.dev/skills/nschneir/project64/c64-development"><img src="https://agentmods.dev/badge/skills/nschneir/project64/c64-development.svg" alt="Measured on agentmods" 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 | $0.00078 | $0.09470 |
| Opus 5 | $0.00039 | $0.04735 |
| Sonnet 5 | $0.00016 | $0.01894 |
| Haiku 4.5 | $0.00008 | $0.00947 |
Grade A, and why
c64-development 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 3d 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.
The source is not reproduced here
No licence file
A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.
What ships with it
8 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.
- 3d ago First seen · 579 lines · 78 tokens per session scan A 56686eaabe56
c64-development is a skill published in the GitHub repository nschneir/Project64 (2 stars, last pushed 11d ago), with no licence file. It adds 78 tokens to every session and 9,470 once invoked, about $0.0004 per session on Opus 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.
Other skills, from other repositories
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Use when writing or debugging 6502 assembly for the Commodore PET with ca65/ld65 via pet build or pet run. Covers the PET program skeleton, the BASIC SYS stub, calling ROM routines, and 6502 gotchas.
pet-development
Use when developing, running, or debugging Commodore PET software (Commodore BASIC or 6502 assembly) on the VICE emulator with the pet CLI or the pet-tools MCP server. Covers the build/run/observe/debug loop, the stopped-state discipline, PET text encodings, and per-model differences.
6502-debugging
Use when a PET program misbehaves at runtime — crashes, corruption, wrong values, dead input, visual glitches — and you need a procedure, not a guess. Symptom-indexed playbook of runtime debugging procedures using pet-tools.
hello-world
Run the fastest greeting or smoke-test path across VICE and C64U.
basic-program
Execute bespoke Commodore BASIC v2 programs through c64bridge.
assembly-program
Execute 6502/6510 assembly workflows through c64bridge.