seo-performance

seo-performance is an agent for Claude Code from Gekkos-tech/agency-os. It costs 18 tokens per session (907 once invoked), scanned A, a copy of seo-performance, MIT.

A web-performance analysis agent that measures how quickly pages load, respond to interaction, and settle visually. It uses Core Web Vitals, the standard user-focused measures for page speed and stability.

In plain words
What is it for?
Use it to analyze a page’s LCP, INP, and CLS scores and recommend concrete improvements to loading, interaction speed, and visual stability.
Why use it?
It replaces guesses about slow websites with measured results and prioritized fixes. It helps identify issues such as large images, blocking scripts, slow servers, and shifting page layouts.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: model in frontmatter.

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is python3 scripts/pagespeed_check.py URL --json.

Part of the seo-marketing plugin — 11 agents shipped together

Good fit Use it to analyze a page’s LCP, INP, and CLS scores and recommend concrete improvements to loading, interaction speed, and visual stability.

Compare 6 agents from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/Gekkos-tech/agency-os
agentmods
npx agentmods add agents/gekkos-tech/agency-os/seo-performance

Made for: Claude Code.

Or install seo-marketing, the plugin that ships this one along with the rest of its 11 agents.

Wrote 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.

agentmods badge for seo-performance

README.md
[![agentmods](https://agentmods.dev/badge/agents/gekkos-tech/agency-os/seo-performance/github.svg)](https://agentmods.dev/agents/gekkos-tech/agency-os/seo-performance)
Your own site
<a href="https://agentmods.dev/agents/gekkos-tech/agency-os/seo-performance"><img src="https://agentmods.dev/badge/agents/gekkos-tech/agency-os/seo-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.

agentmods 80×15 button for seo-performance

Your own site · 80×15
<a href="https://agentmods.dev/agents/gekkos-tech/agency-os/seo-performance"><img src="https://agentmods.dev/badge/agents/gekkos-tech/agency-os/seo-performance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 18 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 907 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 88% copy Near-identical to another mod in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00018 $0.00907
Opus 5 $0.00009 $0.00453
Sonnet 5 $0.00004 $0.00181
Haiku 4.5 $0.00002 $0.00091

Measured 9d ago against content hash 3c9e56d22de8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

seo-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 9d 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.

Origin

This is a copy

88% identical to seo-performance — 26 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

plugins/seo-marketing/agents/seo-performance.md · 100 lines

How it starts

The opening of the file, as written. The whole thing — 100 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a Web Performance specialist focused on Core Web Vitals.

Current Metrics (as of 2026)

Metric Good Needs Improvement Poor
LCP (Largest Contentful Paint) ≤2.5s 2.5s–4.0s >4.0s
INP (Interaction to Next Paint) ≤200ms 200ms–500ms >500ms
CLS (Cumulative Layout Shift) ≤0.1 0.1–0.25 >0.25

IMPORTANT: INP replaced FID on March 12, 2024. FID was fully removed from all Chrome tools (CrUX API, PageSpeed Insights, Lighthouse) on September 9, 2024. INP is the sole interactivity metric. Never reference FID.

Evaluation Method

Google evaluates the 75th percentile of page visits, 75% of visits must meet the "good" threshold to pass.

When Analyzing Performance

  1. Use PageSpeed Insights API if available
  2. Use python3 scripts/render_page.py <URL> --mode auto --json before HTML/source inspection so SPA content is visible when needed
  3. Provide specific, actionable optimization recommendations
  4. Prioritize by expected impact

Common LCP Issues

  • Unoptimized hero images (compress, WebP/AVIF, preload)
  • Render-blocking CSS/JS (defer, async, critical CSS)
  • Slow server response TTFB >200ms (edge CDN, caching)
  • Third-party scripts blocking render
  • Web font loading delay

Common INP Issues

  • Long JavaScript tasks on main thread (break into <50ms chunks)
  • Heavy event handlers (debounce, requestAnimationFrame)
  • Excessive DOM size (>1,500 elements)
  • Third-party scripts hijacking main thread
  • Synchronous operations blocking

Common CLS Issues

  • Images without width/height dimensions
  • Dynamically injected content
  • Web fonts causing FOIT/FOUT
  • Ads/embeds without reserved space
  • Late-loading elements

Performance Tooling (2025-2026)

Lighthouse 13.0 (October 2025): Major audit restructuring with reorganized performance categories and updated scoring weights. Use as a lab diagnostic tool: always validate against CrUX field data for real-world performance.

Read the full file on GitHub · 100 lines

Changes

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.

  1. 9d ago First seen · 100 lines · 18 tokens per session scan A 3c9e56d22de8

Subscribe to this mod's changes

seo-performance is an agent published in the GitHub repository Gekkos-tech/agency-os (5 stars, last pushed 1mo ago), licensed MIT. It adds 18 tokens to every session and 907 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 88% identical to seo-performance, differing in 26 lines, and is treated as a copy.

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