sc-markers

sc-markers is a skill for Claude Code, Codex from TianGzlab/OmicsClaw. It costs 61 tokens per session (2,182 once invoked), scanned A, original, Apache-2.0.

A tool that ranks genes that distinguish each existing cell cluster or cell-type group. These marker genes provide evidence for understanding what each group represents.

In plain words
What is it for?
Finding marker genes for clusters or labelled cell groups using statistical tests or specificity scoring.
Why use it?
It turns clustered single-cell data into an ordered list of characteristic genes, without requiring you to inspect every gene manually.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Finding marker genes for clusters or labelled cell groups using statistical tests or specificity scoring.

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Install with agentmods
npx agentmods add skills/tiangzlab/omicsclaw/sc-markers
Install

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.

Any agent
npx skills add TianGzlab/OmicsClaw --skill sc-markers
Clone the repo
git clone --depth 1 https://github.com/TianGzlab/OmicsClaw

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for sc-markers

README.md
[![agentmods](https://agentmods.dev/badge/skills/tiangzlab/omicsclaw/sc-markers/github.svg)](https://agentmods.dev/skills/tiangzlab/omicsclaw/sc-markers)
Your own site
<a href="https://agentmods.dev/skills/tiangzlab/omicsclaw/sc-markers"><img src="https://agentmods.dev/badge/skills/tiangzlab/omicsclaw/sc-markers/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.

agentmods 80×15 button for sc-markers

Your own site · 80×15
<a href="https://agentmods.dev/skills/tiangzlab/omicsclaw/sc-markers"><img src="https://agentmods.dev/badge/skills/tiangzlab/omicsclaw/sc-markers.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,182 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00061 $0.02182
Opus 5.5 $0.00024 $0.00873
Sonnet 5.5 $0.00012 $0.00436
Haiku 4.5 $0.00006 $0.00218

Measured 14d ago against content hash b4e08fe60b26, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

sc-markers 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 14d ago.

The scan reads SKILL.md. This mod also ships 5 executable files (_api.py, examples/example_step.py, sc_markers.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

skills/singlecell/scrna/sc-markers/SKILL.md · 187 lines

How it starts

The opening of the file, as written. The whole thing — 187 lines — stays where its author put it; the contents beside it link to each section on GitHub.

sc-markers

When to use

The user already has clustering / cell-type labels in obs (typically leiden, louvain, or cell_type) and wants ranked marker genes per group as evidence for downstream annotation or interpretation. Four methods: wilcoxon (default rank-sum), t-test (Welch), logreg (multinomial logistic regression — discriminative ranking), cosg (fast cosine-specificity scoring without p-values). This is for cluster markers, not condition contrasts — for treatment-vs-control DE with replicates use sc-de.

Use from a step

markers = load_skill("sc-markers")
adata = read_input("results/02_cluster/intermediate/adata_clustered.h5ad")
table = markers.find_markers(adata, groupby="leiden")
write_output(table, "tables/markers_all.csv")
write_output(markers.top_markers(table), "tables/markers_top.csv")
write_output(markers.run_info(table), "tables/marker_run.json")

A complete step on log-normalized PBMC expression is in examples/example_step.py.

API

find_markers(adata, *, groupby: str, method: str='wilcoxon', n_genes: int | None=None, min_in_group_fraction: float=0.25, min_fold_change: float=0.25, max_out_group_fraction: float=0.5, mu: float=1.0) -> pd.DataFrame

Rank marker genes for each group against the rest using adata.X.

X should contain normalized expression. Computation uses a copy, so the input's matrices, obs and uns are unchanged. Scanpy methods apply the expression-fraction and fold-change filters; when filtering fails or removes every row, the unfiltered ranking is returned and run_info records filter_fallback and its reason. COSG scores specificity without p-values.

:param groupby: The obs column defining clusters or cell types. :param method: wilcoxon (default), t-test, logreg or cosg. :param n_genes: Genes ranked per group. None means all genes for Scanpy methods and 50 for COSG, matching the CLI defaults. :param min_in_group_fraction: Minimum expressing fraction within a group. Default 0.25; unused by COSG. :param min_fold_change: Fold-change filter passed to Scanpy. Default 0.25; unused by COSG. :param max_out_group_fraction: Maximum expressing fraction outside a group. Default 0.5; unused by COSG. :param mu: COSG specificity penalty. Default 1.0; unused by Scanpy methods. :returns: A DataFrame with group, names, scores and method-dependent effect, p-value and fraction columns. COSG pvals and pvals_adj are NaN. The table's attrs hold the run record; use run_info before CSV export. :raises ValueError: Unknown method or missing grouping column.

Read the full file on GitHub · 187 lines

Files

What ships with it

9 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.

Changes

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.

  1. 14d ago Changed · +76 lines scan C → A b4e08fe60b26
  2. 1mo ago First seen · 111 lines · 61 tokens per session scan C 42658b2004b6

Subscribe to this mod's changes

sc-markers is a skill published in the GitHub repository TianGzlab/OmicsClaw (161 stars, last pushed 14d ago), licensed Apache-2.0. It adds 61 tokens to every session and 2,182 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 2026-09-03.

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