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 fullstack-phoenix/saas_kit --skill fun-with-flagsgit clone --depth 1 https://github.com/fullstack-phoenix/saas_kitWrote 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/fullstack-phoenix/saas_kit/fun-with-flags)<a href="https://agentmods.dev/skills/fullstack-phoenix/saas_kit/fun-with-flags"><img src="https://agentmods.dev/badge/skills/fullstack-phoenix/saas_kit/fun-with-flags/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/fullstack-phoenix/saas_kit/fun-with-flags"><img src="https://agentmods.dev/badge/skills/fullstack-phoenix/saas_kit/fun-with-flags.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 | $0.00054 | $0.01301 |
| Opus 5.5 | $0.00022 | $0.00520 |
| Sonnet 5.5 | $0.00011 | $0.00260 |
| Haiku 4.5 | $0.00005 | $0.00130 |
Grade A, and why
fun-with-flags 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 2mo 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 — 141 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Feature flags with FunWithFlags
Wires FunWithFlags into the app with the Ecto persistence adapter and Phoenix
PubSub cache notifications, so flags toggle at runtime without a deploy. Adds two
app-owned wrapper modules — MyApp.Feature for application code and
MyAppWeb.FeatureFlags for conns/sockets/assigns — plus a web admin UI for
managing flags. When authentication or teams are installed, it generates the
FunWithFlags.Actor implementations needed to gate flags per user and per team.
When to use
- The app needs to turn features on/off at runtime without a deploy or restart.
- You want gradual rollouts (enable a flag for specific users or teams first).
- You need an emergency kill switch for a misbehaving feature.
- Don't reach for this for static, compile-time config — use
config/*.exsinstead. Flags add a DB table and runtime lookups.
Dependencies
- Requires: None.
- Recommended: None. Install
authenticationfirst if you want per-user gating, andteamsfor per-team gating — the actor implementations are generated only when those features are present.
Install
mix saaskit.feature.install fun_with_flags
No install decisions. Behavior adapts to what's already installed:
- With
admin: mounts the flag UI at/admin/feature-flagsbehind:require_authenticated_user+:require_admin_user, and adds a link on the admin developer page. Withoutadmin: mounts an unguarded UI at/feature-flags. - With
authentication: generateslib/my_app/feature_actor/user.ex. - With
teams: generateslib/my_app/feature_actor/team.ex.
What it generates
lib/my_app/feature.ex—MyApp.Feature.enabled?/2, the domain-level API. Resolves a%{team:, user:}scope and OR's the team and user gates.lib/my_app_web/feature_flags.ex—MyAppWeb.FeatureFlags.enabled?/2, accepts a conn, LiveView socket, or assigns map and forwards:current_scope.lib/my_app/feature_actor/user.ex—FunWithFlags.Actorimpl forUser(only withauthentication).lib/my_app/feature_actor/team.ex—FunWithFlags.Actorimpl forTeam(only withteams).- Migration
priv/repo/migrations/*_create_feature_flags_table.exs— creates thefun_with_flags_togglestable with the configured primary-key type. - Router scope mounting
FunWithFlags.UI.Router. - Adds
:fun_with_flagsand:fun_with_flags_uitomix.exs.
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.
- 2mo ago First seen · 141 lines · 54 tokens per session scan A 009f09133322
fun-with-flags is a skill published in the GitHub repository fullstack-phoenix/saas_kit (2 stars, last pushed 4mo ago), licensed MIT. It adds 54 tokens to every session and 1,301 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 2026-08-31.
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