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 vinzscam/backstage-skills --skill creating-backstage-entity-page-extensiongit clone --depth 1 https://github.com/vinzscam/backstage-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/vinzscam/backstage-skills/creating-backstage-entity-page-extension)<a href="https://agentmods.dev/skills/vinzscam/backstage-skills/creating-backstage-entity-page-extension"><img src="https://agentmods.dev/badge/skills/vinzscam/backstage-skills/creating-backstage-entity-page-extension/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/vinzscam/backstage-skills/creating-backstage-entity-page-extension"><img src="https://agentmods.dev/badge/skills/vinzscam/backstage-skills/creating-backstage-entity-page-extension.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 | $0.00111 | $0.01029 |
| Opus 5 | $0.00056 | $0.00515 |
| Sonnet 5 | $0.00022 | $0.00206 |
| Haiku 4.5 | $0.00011 | $0.00103 |
Grade A, and why
creating-backstage-entity-page-extension 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 11d 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 — 52 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Creating Catalog Entity Page Extensions
When to use this skill
- Adding a card to the Overview tab of a catalog entity (e.g. "show Jira project info on Components linked to a Jira project")
- Adding a whole tab (a content panel with its own URL path) to a catalog entity page (e.g. "/incidents" tab on Components, listing the component's incidents)
- Filtering when an extension appears, based on entity kind, spec type, annotation presence, or any custom predicate
This is the most common reason to scaffold a frontend-plugin-module. The plugin you're authoring extends the host's catalog plugin via these blueprints.
Choose the right pattern
| Building... | Pattern | Reference |
|---|---|---|
| A card on the entity Overview tab | EntityCardBlueprint.make({ name, params: { loader, filter?, type? } }) |
references/card.md |
| A full tab (its own URL path) on the entity page | EntityContentBlueprint.make({ name, params: { path, title, loader, filter?, group?, icon? } }) |
references/content.md |
Both blueprints come from @backstage/plugin-catalog-react/alpha. They share:
- A
loader: () => Promise<JSX.Element>for code-splitting the rendered component. - A
filterparameter that controls when the extension appears (see "Entity filtering" below). - The component renders inside the catalog entity context — read the current entity via
useEntity()from@backstage/plugin-catalog-react.
Two invocation modes
- Standalone: editing an existing
frontend-plugin-modulethat targets the catalog. Pick the right reference (card or content) and add the extension. - Post-scaffold (called by
creating-backstage-pluginforfrontend-plugin-moduletemplates targetingcatalog): scaffold the extension(s) the user described, plus the component(s) they render.
What ships with it
2 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.
- 11d ago First seen · 52 lines · 111 tokens per session scan A e99f193f38b1
creating-backstage-entity-page-extension is a skill published in the GitHub repository vinzscam/backstage-skills (4 stars, last pushed 16d ago), licensed Apache-2.0. It adds 111 tokens to every session and 1,029 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 2026-08-31.
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