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 K-Dense-AI/drug-discovery-agent-skills --skill retrosynthesisgit clone --depth 1 https://github.com/K-Dense-AI/drug-discovery-agent-skillsWrote 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/k-dense-ai/drug-discovery-agent-skills/retrosynthesis)<a href="https://agentmods.dev/skills/k-dense-ai/drug-discovery-agent-skills/retrosynthesis"><img src="https://agentmods.dev/badge/skills/k-dense-ai/drug-discovery-agent-skills/retrosynthesis/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/k-dense-ai/drug-discovery-agent-skills/retrosynthesis"><img src="https://agentmods.dev/badge/skills/k-dense-ai/drug-discovery-agent-skills/retrosynthesis.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00122 | $0.01828 |
| Opus 5 | $0.00061 | $0.00914 |
| Sonnet 5 | $0.00024 | $0.00366 |
| Haiku 4.5 | $0.00012 | $0.00183 |
Grade A, and why
retrosynthesis 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 12d 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 — 155 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Retrosynthetic Planning
The Make half of design-make-test-analyse, and the check that a proposed molecule is more than a picture. AiZynthFinder runs Monte Carlo tree search over reaction templates until every leaf of a route is something you can buy.
Tool: AiZynthFinder 4.4.1, MIT.
pip install aizynthfinder — Python 3.10–3.12 only, it will not install on 3.13. Then
download_public_data <dir> for models and a ZINC stock (several GB). CPU is sufficient.
Checked against: 4.4.1, December 2025.
Read references/aizynthfinder-setup.md before your first run, references/synthesizability-scores.md when triaging more molecules than you can search, and references/route-quality.md before acting on a route — that one is judgement, not syntax.
The two scripts
| Script | Answers |
|---|---|
aizynth_config.py |
What does the config look like, and are the model files really there? |
route_report.py |
What fraction is makeable, in how many steps, from what? |
The stock file is the answer
This is the thing to get right. A target is solved when every leaf of a route is in your stock file — so "solved" is a statement about the stock at least as much as about the molecule.
| Stock | Solved fraction |
|---|---|
| small in-house inventory | low; reflects what you can start today |
| ZINC (the default download) | moderate; a public baseline |
| eMolecules / commercial | high |
| Enamine building blocks | high; what a REAL-space campaign should use |
A solved fraction quoted without naming the stock is meaningless — the same molecule is solved
against eMolecules and unsolved against a cupboard. route_report.py says so on every run.
Configuration changed at version 4
Version 3 took bare lists of file paths; version 4 takes typed blocks. Every tutorial older than 2024 shows the incompatible form, and the resulting error is unhelpful.
What ships with it
5 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.
- 12d ago First seen · 155 lines · 122 tokens per session scan A cca58d59c1fe
retrosynthesis is a skill published in the GitHub repository K-Dense-AI/drug-discovery-agent-skills (28 stars, last pushed 5d ago), licensed MIT. It adds 122 tokens to every session and 1,828 once invoked, about $0.0006 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 2026-08-30.
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