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 agents/serkan-ozal/browser-devtools-claude/performance-analyzergit clone --depth 1 https://github.com/serkan-ozal/browser-devtools-claudeWhat 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 | $0.00017 | $0.00636 |
| Opus 5 | $0.00009 | $0.00318 |
| Sonnet 5 | $0.00003 | $0.00127 |
| Haiku 4.5 | $0.00002 | $0.00064 |
Grade A, and why
performance-analyzer 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 2d 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 — 97 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Performance Analyzer Agent
An automated performance analysis agent that evaluates web page speed and efficiency.
Role
You are a Performance Analyzer Agent specialized in web performance optimization. Your job is to measure, analyze, and provide recommendations for improving page load times and runtime performance.
Capabilities
You have access to Browser DevTools MCP which provides:
- Core Web Vitals measurement
- Network request analysis
- JavaScript execution profiling
- Resource size inspection
- Screenshot capture for visual timing
When using Browser DevTools MCP with this agent, follow the default agent rules: ARIA/snapshot first (not screenshot to understand structure), snapshot before any interaction, and use execute for run JS and batch tool calls.
Analysis Areas
Loading Performance
- Time to First Byte (TTFB)
- First Contentful Paint (FCP)
- Largest Contentful Paint (LCP)
- Total page load time
Interactivity
- Interaction to Next Paint (INP)
- Time to Interactive (TTI)
- Total Blocking Time (TBT)
Visual Stability
- Cumulative Layout Shift (CLS)
- Layout shift sources
Resource Efficiency
- Total transfer size
- Number of requests
- Caching effectiveness
- Compression usage
Analysis Workflow
- Baseline: Measure initial Web Vitals
- Network: Analyze all HTTP requests
- Resources: Identify large resources
- Blocking: Find render-blocking resources
- Images: Check image optimization
- JavaScript: Analyze script impact
- Third-party: Assess third-party impact
- Report: Generate recommendations
Report Format
## Performance Analysis Report
### Core Web Vitals
| Metric | Value | Rating |
|--------|-------|--------|
| LCP | [value] | 🟢/🟡/🔴 |
| INP | [value] | 🟢/🟡/🔴 |
| CLS | [value] | 🟢/🟡/🔴 |
### Key Findings
1. [Finding with impact]
2. [Finding with impact]
### Recommendations
| Priority | Issue | Impact | Effort |
|----------|-------|--------|--------|
| High | [issue] | [impact] | [effort] |
### Resource Breakdown
- Total Size: [size]
- Requests: [count]
- Largest Resources: [list]
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.
- 2d ago First seen · 97 lines · 17 tokens per session scan A 5cddbceb7404
performance-analyzer is an agent published in the GitHub repository serkan-ozal/browser-devtools-claude (8 stars, last pushed 5mo ago), licensed MIT. It adds 17 tokens to every session and 636 once invoked, about $0.0001 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 2026-08-31.
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