GSC Content Decay — 90-Day Decline Detection

@skills/seo/references/mcp-degradation.md @skills/seo/references/gsc-api-reference.md

Identifies pages experiencing true content decay: both clicks AND impressions declining over a 90-day comparison period. Filters out seasonal variation by requiring both metrics to decline simultaneously.

MCP Check

Before calling any GSC tool, verify the MCP is connected:

1. Use ToolSearch with query +google-search-console
2. If tools returned — note the actual tool name prefix, proceed to Inputs
3. If no tools returned — display the GSC MCP error template from references/mcp-degradation.md and stop:

## Google Search Console MCP Not Available

The `/seo gsc content-decay` command requires the GSC MCP, which is not currently connected.

**What you can do:**
- Use `/seo technical <url>` for crawlability and indexability analysis (no live data)
- Use `/seo audit <url>` for a full static SEO audit

**To connect GSC MCP:**
- Install and configure a Google Search Console MCP server (see README for setup)
- Add it to ~/.claude/mcp.json at user scope (NOT project scope)
- Verify GSC property access before running commands (domain vs URL prefix format)
- See references/gsc-api-reference.md for property format details

Inputs

• site: The GSC property URL. Accept both formats:
  • Domain property: sc-domain:example.com
  • URL prefix: https://example.com or https://www.example.com
  • If user provides a bare domain (no prefix), call list_sites to identify the correct property format registered in GSC.

Date Calculation

Use Bash to calculate 90-day comparison windows (GSC has ~3 day delay):

currentEnd=$(date -v-3d +%Y-%m-%d)
currentStart=$(date -v-93d +%Y-%m-%d)
previousEnd=$(date -v-93d +%Y-%m-%d)
previousStart=$(date -v-183d +%Y-%m-%d)
echo "Current: $currentStart to $currentEnd | Previous: $previousStart to $previousEnd"

Execution

Call compare_performance with 90-day window:

• siteUrl: the site property
• currentStartDate: currentStart
• currentEndDate: currentEnd
• previousStartDate: previousStart
• previousEndDate: previousEnd
• dimension: "page"
• limit: 1000

Post-processing — identify true decay: Filter results to rows where BOTH conditions are true:

1. clicksChange < 0 (clicks declined)
2. Impressions declined (if impressionsChange field available, check impressionsChange < 0; if not available, use the presence of lower current impressions vs previous)

This double-filter removes pages that lost clicks but maintained/grew impressions (which often indicates seasonal or competitor CTR changes, not content decay).

Sort by clicksChangePercent ascending (most severe decay first).

Calculate decay severity: For each decaying page, compute click change percentage if not provided: changePercent = abs(clicksChange / previousClicks) * 100

Severity classification:

• changePercent > 50: CRITICAL
• changePercent >= 30 and <= 50: HIGH
• changePercent >= 10 and < 30: MEDIUM

Recommendation per page based on position change:

• Position declined significantly (positionChange > 5): "Review competitor content — rankings lost"
• Position stable but impressions fell: "Check for technical issues — may have indexing problems"
• Position slightly declined (positionChange 1-5): "Update and refresh content to regain relevance"
• Position improved but clicks fell: "Review search intent — content may no longer match query intent"

CTR display rule: API returns CTR as decimal — multiply by 100 for display.

Output Format

## GSC Content Decay: [site property]
**Current Period:** [currentStart] to [currentEnd] (90 days)
**Previous Period:** [previousStart] to [previousEnd] (90 days)
**Decay pages found:** [count]

### Content Decay Report
| Decay Severity | URL | Current Clicks | Previous Clicks | Change% | Curr Position | Prev Position | Pos Change | Action |
|----------------|-----|---------------|-----------------|---------|---------------|---------------|------------|--------|
| CRITICAL | [url] | [n] | [n] | -X.X% | [X.X] | [X.X] | ↑/↓ X.X | [action] |
| HIGH | [url] | [n] | [n] | -X.X% | [X.X] | [X.X] | ↑/↓ X.X | [action] |
| MEDIUM | [url] | [n] | [n] | -X.X% | [X.X] | [X.X] | ↑/↓ X.X | [action] |
...

### Summary by Severity
| Severity | Pages | Avg Click Loss |
|----------|-------|----------------|
| CRITICAL (>50% drop) | [n] | [X.X%] |
| HIGH (30-50% drop) | [n] | [X.X%] |
| MEDIUM (10-30% drop) | [n] | [X.X%] |

Truncate long URLs to 60 characters with ... for readability. If no decay pages found, report: "No content decay detected. No pages show simultaneous decline in both clicks and impressions over the 90-day comparison period."