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 majiayu000/spellbook --skill performance-capacitygit clone --depth 1 https://github.com/majiayu000/spellbookWrote 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/majiayu000/spellbook/performance-capacity)<a href="https://agentmods.dev/skills/majiayu000/spellbook/performance-capacity"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/performance-capacity/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/majiayu000/spellbook/performance-capacity"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/performance-capacity.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00075 | $0.00422 |
| Opus 5 | $0.00037 | $0.00211 |
| Sonnet 5 | $0.00015 | $0.00084 |
| Haiku 4.5 | $0.00007 | $0.00042 |
Grade A, and why
performance-capacity 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 8d 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.
What it actually says
Performance Capacity
Purpose
Use this skill to make performance measurable before optimizing. It turns vague "make it faster" work into budgets, probes, bottleneck hypotheses, and regression gates.
Baseline First
Before changing code, capture:
- User-facing operation or background job under test.
- Current p50/p95/p99 latency or throughput.
- Data size and concurrency assumptions.
- Resource limits: CPU, memory, IO, network, database, queue.
- Existing cache behavior and invalidation rules.
- Cost or quota constraints.
If no baseline can be gathered, state the nearest measurable proxy and its limitations.
Budget Design
Define budgets by surface:
| Surface | Examples |
|---|---|
| UI | TTI, interaction latency, bundle size, render count |
| API | p95 latency, error rate, DB query count, payload size |
| Jobs | throughput, max lag, retry cost, idempotency |
| Data | query plan, index coverage, backfill duration |
| Infra | CPU/RSS, concurrency, autoscaling, cost per request |
Optimization Rules
- Optimize the measured bottleneck, not the most familiar code.
- Prefer algorithmic, query, batching, and cache correctness fixes before capacity-only fixes.
- Define cache invalidation and stale-data tolerance.
- Add a regression test, benchmark, or dashboard check for risky paths.
- Do not trade correctness, authorization, or tenant isolation for speed.
Output Shape
operation:
baseline:
target_budget:
bottleneck_hypothesis:
measurement_plan:
optimization_options:
capacity_estimate:
regression_gate:
verification_commands:
What ships with it
1 file 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.
- 8d ago First seen · 58 lines · 75 tokens per session scan A a20f17ad4866
performance-capacity is a skill published in the GitHub repository majiayu000/spellbook (278 stars, last pushed today), licensed MIT. It adds 75 tokens to every session and 422 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 2026-09-03.
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