Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add haabe/mycelium/plugin install myceliumWrote 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/haabe/mycelium/a11y-check)<a href="https://agentmods.dev/skills/haabe/mycelium/a11y-check"><img src="https://agentmods.dev/badge/skills/haabe/mycelium/a11y-check/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/haabe/mycelium/a11y-check"><img src="https://agentmods.dev/badge/skills/haabe/mycelium/a11y-check.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 | $0.00065 | $0.01790 |
| Opus 5 | $0.00032 | $0.00895 |
| Sonnet 5 | $0.00013 | $0.00358 |
| Haiku 4.5 | $0.00006 | $0.00179 |
Grade A, and why
a11y-check 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 3d 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 — 129 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Accessibility Audit
Evaluate user-facing work against the criteria that BIND TO ITS SURFACES. Accessibility is a design constraint, not a polish step (Downe Principle 11) — and an instrument aimed at a surface the product does not have measures nothing while looking like a failure.
STEP 1 — SURFACE GATE. Run this BEFORE the checklist, every time.
The checklist below is written for web pages. Most products are not web pages. Detect which
user-facing surfaces this product actually has, from the repository, and evaluate ONLY the criteria
that bind to them. Profiles and detection hints: engine/canvas-guidance.yml#surfaces —
web · rendered_markdown · terminal · native_app · video_audio · document · headless.
A product commonly has several. State which you found and how, in the output.
THE RULE THAT DECIDES EVERY RATING:
| situation | rating |
|---|---|
| the surface is ABSENT | n/a — and say which surface is missing |
| the surface is PRESENT and you measured it | pass / partial / fail on the evidence |
| the surface is PRESENT and you did NOT measure it | not-assessed — a real gap, it could have been measured |
MARKING A CRITERION fail BECAUSE ITS SURFACE DOES NOT EXIST IS A CATEGORY ERROR. It
manufactures a defect out of a product's shape, and a done-bar built on it fails for a reason no
work can fix.
MEASURED, WHICH IS WHY THIS SECTION EXISTS. On 2026-09-03 this skill's checklist was applied to
Mycelium — a terminal product with markdown docs — and Downe principle 11 was rated fail, with
the entry stating plainly: "NOT TESTED, which is this principle's own fail criterion... WCAG 2.1 AA
is largely the wrong instrument for a terminal product." A delivery bar failed on an instrument
that could not bind. Re-run 2026-09-04 under the surface gate: every applicable criterion passed,
and the rest were n/a by absence of surface rather than unmeasured.
THREE CONSTRAINTS, OR THIS GATE BECOMES A WAIVER MACHINE. Declaring a surface costs work; declaring its absence costs a word, and accessibility has a long history of being waived on exactly such grounds.
- Detect from artifacts and RECORD THE EVIDENCE — say what you looked for and where. An
n/awhose basis is "the agent decided" is not a finding and cannot be falsified later. n/amust never read aspassin a total. "6 pass / 3 n/a" is honest; "9 of 15 clear" is the thing this rule exists to stop.- FLOOR: every shipped product has at least one human surface — its docs, at minimum. A
fully-
n/aaccessibility result is a DETECTOR BUG, not a clean bill. Treat that run as broken.
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.
- 3d ago Changed · +51 lines · +32 tokens per session d14f79b2ae3e
- 9d ago First seen · 78 lines · 33 tokens per session scan A d3b458607483
a11y-check is a skill published in the GitHub repository haabe/mycelium (45 stars, last pushed 2d ago), licensed MIT. It adds 65 tokens to every session and 1,790 once invoked, about $0.0003 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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