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 rules/netlify/context-and-tools/netlify-image-cdngit clone --depth 1 https://github.com/netlify/context-and-toolsWrote 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/netlify/context-and-tools/netlify-image-cdn)<a href="https://agentmods.dev/rules/netlify/context-and-tools/netlify-image-cdn"><img src="https://agentmods.dev/badge/rules/netlify/context-and-tools/netlify-image-cdn.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 | $0.00127 | $0.02110 |
| Opus 5 | $0.00063 | $0.01055 |
| Sonnet 5 | $0.00025 | $0.00422 |
| Haiku 4.5 | $0.00013 | $0.00211 |
Grade C, and why
netlify-image-cdn scanned grade C with 2 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 4d 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.
Hidden instructionshighPrompt injection
Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.
<!-- system: agent-context/image-cdn/system.md — human-owned, merged by ctx-gen; edit system.md, not this section --> Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -vs 'https://mysitename.netlify.app/.netlify/images?url=/owl.jpeg&fit=cover&w=50&h=50&position=left&fm=webp&q=80' How it starts
The opening of the file, as written. The whole thing — 161 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Netlify Image CDN
Transform images by requesting /.netlify/images with query parameters. No function or file authoring required — it's a built-in edge endpoint.
# resize + crop to a 50px square, retain left side, convert to webp at q=80
curl -vs 'https://mysitename.netlify.app/.netlify/images?url=/owl.jpeg&fit=cover&w=50&h=50&position=left&fm=webp&q=80'
There is no legacy/deprecated form — the endpoint above is the only programmatic surface. Use framework image components where available (below) rather than hand-building URLs.
Endpoint & query parameters
GET /.netlify/images?url=<source>&...
| Param | Values | Notes |
|---|---|---|
url |
relative path or full remote URL | REQUIRED. Only required param. |
w |
integer px | width |
h |
integer px | height |
fit |
contain (default), cover, fill |
resize behavior |
position |
center (default), top, bottom, left, right |
only applies when fit=cover |
fm |
avif, jpg, png, webp, gif, blurhash |
output format; webp/gif can be animated |
q |
integer 1–100 (default 75) |
only for avif, jpg, gif, webp |
fit behavior
fit= |
aspect ratio kept | crops excess | returns exact dimensions |
|---|---|---|---|
contain |
yes | no | no — one dimension may be smaller |
cover |
no | yes | yes — scaled proportionally, then cropped |
fill |
no | no | yes — stretched/squished if needed |
fit=coverrequires BOTHwandh. Supplying only one silently misbehaves.containwith one dimension calculates the other to preserve aspect ratio.
Format & content negotiation
- Source-only request (just
url, no size/format): image is unchanged in size/shape but still reformatted toavif/webpbased on the browser'sAcceptheader. - No
fmspecified →webpif accepted, elseavifif accepted, else original. fm=blurhashreturns a BlurHash text string, not image bytes. Pointing<img src>or a CSS background at it renders nothing. Fetch the string server-side/ahead of time, decode it client-side with a BlurHash library (https://blurha.sh), then load the real image as a separate request withoutfm=blurhash.
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.
- 4d ago First seen · 161 lines · 127 tokens per session scan C 942cd5d77d18
netlify-image-cdn is a cursor rule published in the GitHub repository netlify/context-and-tools (36 stars, last pushed 7d ago), licensed MIT. It adds 127 tokens to every session and 2,110 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it C with 2 findings (hidden instructions, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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