Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/twells89/sigma-migration-skillsnpx agentmods add rules/twells89/sigma-migration-skills/sigma-plugin-authoringWrote 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/rules/twells89/sigma-migration-skills/sigma-plugin-authoring)<a href="https://agentmods.dev/rules/twells89/sigma-migration-skills/sigma-plugin-authoring"><img src="https://agentmods.dev/badge/rules/twells89/sigma-migration-skills/sigma-plugin-authoring/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/rules/twells89/sigma-migration-skills/sigma-plugin-authoring"><img src="https://agentmods.dev/badge/rules/twells89/sigma-migration-skills/sigma-plugin-authoring.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 | $0.00192 | $0.02837 |
| Opus 5 | $0.00096 | $0.01418 |
| Sonnet 5 | $0.00038 | $0.00567 |
| Haiku 4.5 | $0.00019 | $0.00284 |
Grade A, and why
sigma-plugin-authoring 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 8d 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 — 191 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Build, register, host, embed, and data-bind a bespoke Sigma custom plugin (@sigmacomputing/plugin) to recreate a source visualization for which Sigma has no native chart/KPI/table equivalent — a radial gauge, a custom heatmap, a sankey, or any bespoke viz kind outside Sigma's native element set. Use when a source viz has no native Sigma equivalent and should be recreated as a bespoke plugin — not when a native Sigma chart, KPI, or table kind already covers it (that's the
sigma-workbooksskill). Covers the full lifecycle: writing the single-file plugin, registering it viaPOST /v2/plugins, hosting it, embedding it in a workbook spec bound to real data, and verifying value parity. Ships a worked example (a radial gauge / "value vs. target" plugin) and theplugin_embedemitter. Requires an SIGMA_API_TOKEN — obtain via the sigma-api skill first.
Sigma Plugin Authoring (Recreate-as-Plugin)
Sigma's native element kinds (bar-chart, kpi-chart, table, pivot-table,
point-map, …) cover most dashboards. Some source vizzes don't map to any of
them — a radial/semicircle gauge, a calendar heatmap, a sankey, a custom
ring/dial. For those, recreate the viz as a Sigma custom plugin
(@sigmacomputing/plugin): a single-file web app Sigma hosts inside a
workbook element, wired to real workbook data through an editor-panel
contract you define.
Scope
The plugin lifecycle: build → register → host → embed → bind → verify.
Building the rest of the workbook around the plugin (the data table it reads
from, KPIs/controls alongside it, page layout, the hidden data page) is the
sigma-workbooks skill's job — this skill only covers the plugin-specific
pieces. Authoring the underlying data model is sigma-data-models.
Decision: does this viz need a plugin at all?
Before reaching for this skill, confirm there's genuinely no native fit:
check the sigma-workbooks skill's chart/KPI/table reference and, if still
unsure, query the OpenAPI's kind enum (see that skill's "Consulting the
shapes" section). Only recreate as a plugin when the native surface is a
confirmed miss — plugins carry real lifecycle cost (hosting, registration,
re-registration on URL change) that a native chart doesn't.
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.
- 8d ago First seen · 191 lines · 192 tokens per session scan A abc622256209
sigma-plugin-authoring is a cursor rule published in the GitHub repository twells89/sigma-migration-skills (14 stars, last pushed 5d ago), licensed MIT. It adds 192 tokens to every session and 2,837 once invoked, about $0.0010 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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