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 oborchers/fractional-cto --skill caching-and-performancegit clone --depth 1 https://github.com/oborchers/fractional-ctoWrote 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/oborchers/fractional-cto/caching-and-performance)<a href="https://agentmods.dev/skills/oborchers/fractional-cto/caching-and-performance"><img src="https://agentmods.dev/badge/skills/oborchers/fractional-cto/caching-and-performance/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/oborchers/fractional-cto/caching-and-performance"><img src="https://agentmods.dev/badge/skills/oborchers/fractional-cto/caching-and-performance.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 | $0.00076 | $0.02663 |
| Opus 5 | $0.00038 | $0.01332 |
| Sonnet 5 | $0.00015 | $0.00533 |
| Haiku 4.5 | $0.00008 | $0.00266 |
Grade A, and why
caching-and-performance 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 12d 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 — 124 lines — stays where its author put it; the contents beside it link to each section on GitHub.
The Fastest Request Is the One You Never Make
Caching is the highest-leverage performance optimization available to any API. A correctly cached response eliminates network latency entirely, reduces server load, and improves perceived performance by orders of magnitude. Every API endpoint must ship with an explicit caching strategy -- omitting Cache-Control headers forces browsers into heuristic caching, which leads to unpredictable behavior. Start with caching, then layer compression, protocol upgrades, and resilience on top.
Cache-Control Directives
Always set Cache-Control explicitly. Never rely on heuristic caching or the deprecated Expires header.
| Directive | Scope | When to Use |
|---|---|---|
public |
Shared + private caches | Response is identical for all users (product catalogs, reference data, schemas) |
private |
Browser only | Response is user-specific (account details, dashboards). Prevents CDN/proxy caching |
no-cache |
All caches | Cache may store but must revalidate with origin before every use. Use when freshness matters but bandwidth savings from 304s are valuable |
no-store |
All caches | Never cache. Use for financial data, PII, balances, transactions |
max-age=N |
All caches | Response is fresh for N seconds. Primary TTL mechanism for all cacheable responses |
s-maxage=N |
Shared caches only | Overrides max-age for CDNs and proxies. Use to give CDNs longer TTLs than browsers |
must-revalidate |
All caches | Once stale, the cache must not serve the response without revalidating. Prevents serving stale content after TTL expires |
stale-while-revalidate=N |
All caches | Serve stale for N seconds while revalidating in the background. Best single directive for perceived performance on read-heavy endpoints |
immutable |
All caches | Response body will never change for this URL. Skip conditional revalidation entirely. Use for versioned URLs (schemas, configs with version in path) |
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.
- 12d ago First seen · 124 lines · 76 tokens per session scan A a19a19a7f1ad
caching-and-performance is a skill published in the GitHub repository oborchers/fractional-cto (30 stars, last pushed 1mo ago), licensed MIT. It adds 76 tokens to every session and 2,663 once invoked, about $0.0004 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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