1. Technical SEO Audit: What a Proper Site Audit Must Cover

The SEO Agency Services Checklist: How to Vet Technical Audits, On-Page Optimization, and Performance Work

You are about to brief an SEO agency on a technical audit, an on-page optimization campaign, or a site performance overhaul. The difference between a partnership that delivers measurable improvements and one that leaves you with a broken redirect map and a burned domain often comes down to how well you can evaluate the agency’s methodology before you sign. This checklist breaks down the core services—technical SEO audits, on-page optimization, and performance work—into verifiable, risk-aware steps. Use it as a briefing document and a vendor qualification tool.

1. Technical SEO Audit: What a Proper Site Audit Must Cover

A technical SEO audit is not a single crawl report. It is a diagnostic process that examines how search engines discover, render, and index your content, and how well your site infrastructure supports those activities. A credible agency will present an audit that covers at least three layers: crawlability, indexation hygiene, and site infrastructure.

Crawl Budget and Crawlability

Crawl budget refers to the number of URLs Googlebot will crawl on your site within a given timeframe. For large sites (over 10,000 indexed pages), inefficient crawl allocation can leave important pages unindexed for weeks. During an audit, the agency should:

• Analyze server log files (or use a log file analyzer like Screaming Frog Log File Analyser) to see which URLs Googlebot actually requests.
• Compare crawl frequency against page importance. High-value pages (product pages, cornerstone content) should be crawled more often than thin archive pages.
• Identify crawl waste: infinite calendar pages, session-based URLs, filter combinations that generate duplicate paths.

A proper audit will also inspect your `robots.txt` file. A misconfigured `robots.txt` can block entire sections of your site from crawling. The agency should check for:

• Disallow directives that accidentally block important resources (CSS, JS, images).
• Crawl-delay directives that may slow down Googlebot unnecessarily.
• Sitemap references that point to outdated or missing files.

Indexation Hygiene: Sitemaps, Canonicals, and Duplicate Content

Indexation is where most technical audits fail to go deep. A surface-level audit will flag duplicate content warnings. A rigorous audit will trace the source of duplication and recommend a canonicalization strategy.

Checklist item: Verify the XML sitemap coverage. The agency should confirm that the sitemap includes only canonical URLs, excludes paginated pages (unless they are standalone content), and is updated dynamically when pages are added or removed. A static sitemap that was generated six months ago is a red flag.

Checklist item: Review canonical tag implementation. Every page should have a self-referencing canonical tag unless it is a duplicate or a syndicated copy. The audit should identify pages where the canonical tag points to a different domain, an incorrect URL, or is missing entirely.

Checklist item: Quantify duplicate content. The agency should use a tool like DeepCrawl or Sitebulb to cluster pages with high content similarity. They should then propose a remediation plan: merge thin pages, add `noindex` tags to low-value duplicates, or implement rel=canonical for cross-domain duplication.

Site Infrastructure and Core Web Vitals

Core Web Vitals (LCP, CLS, FID/INP) are now part of Google’s ranking system. An audit that does not include a Web Vitals assessment is incomplete. The agency should:

• Measure LCP (Largest Contentful Paint) across mobile and desktop. A target under 2.5 seconds is standard.
• Measure CLS (Cumulative Layout Shift) to identify layout instability caused by late-loading ads, images without dimensions, or web fonts.
• Measure INP (Interaction to Next Paint) to evaluate responsiveness. INP above 200 milliseconds indicates a need for JavaScript optimization.

The audit report should include a table like this:

Risk callout: If the agency proposes quick fixes like lazy-loading all images or removing third-party scripts without testing, push back. Performance improvements should be validated in a staging environment before deployment. A poorly implemented lazy-load can hurt LCP by delaying the initial render.

2. On-Page Optimization: Beyond Meta Tags

On-page optimization is often reduced to keyword stuffing in title tags and meta descriptions. A modern on-page strategy is driven by intent mapping and content structure. When briefing an agency, require them to show how they will approach on-page work for each target page.

Keyword Research and Intent Mapping

Keyword research should not be a one-time exercise. The agency should:

• Cluster keywords by search intent: informational (blog posts, guides), commercial (comparisons, reviews), transactional (product pages, checkout).
• Map each cluster to a specific page type. For example, a commercial intent query like “best SEO agency for e-commerce” should land on a service page with comparison tables, not a blog post.
• Identify keyword gaps where your site has no content for high-volume, high-intent queries.

Checklist item: Ask for a keyword-to-page mapping document. The agency should provide a spreadsheet that lists target keywords, current ranking position, search volume, intent, and the recommended page URL. If the mapping is vague or the same keyword is assigned to multiple pages, the strategy lacks focus.

Content Strategy and Structure

On-page optimization extends to content quality and structure. The agency should audit existing content for:

• Thin content: pages with fewer than 300 words that are not serving a clear purpose (e.g., category pages with no unique description).
• Keyword cannibalization: multiple pages targeting the same primary keyword. The fix is either merging the pages or differentiating the intent.
• Internal linking: a well-structured internal link graph distributes authority from high-authority pages to deeper content. The agency should identify orphan pages (pages with no internal links) and propose a linking plan.

Risk callout: Avoid agencies that promise to rewrite all your content in bulk using AI without human review. Mass rewrites often strip out brand voice, introduce factual errors, and can trigger duplicate content penalties if the AI model was trained on similar source material.

3. Performance Work: Core Web Vitals and Site Speed

Performance optimization is the most technically demanding service an SEO agency can offer. It often requires coordination with your development team. When evaluating an agency’s performance proposal, look for these elements:

Diagnostic Depth

A performance audit should go beyond PageSpeed Insights scores. The agency should:

• Profile your site using Lighthouse, WebPageTest, and Chrome DevTools to identify render-blocking resources, large JavaScript bundles, and inefficient CSS.
• Measure time-to-first-byte (TTFB). A TTFB above 600ms suggests server-side issues that may require CDN or hosting changes.
• Analyze third-party script impact. Each external script (analytics, ads, chatbots) adds load time. The agency should quantify the cost of each script and recommend deferral or removal.

Remediation Plan

The agency should provide a prioritized list of fixes, grouped by effort and impact. For example:

Checklist item: Require a staging test. Do not accept a performance improvement plan that is implemented directly on the live site. The agency should demonstrate the improvements in a staging environment first.

Risk callout: Be wary of agencies that recommend aggressive caching or CDN changes without understanding your content delivery model. An overly aggressive cache policy can prevent dynamic content (e.g., pricing pages, user-specific data) from updating correctly, leading to stale content or broken functionality.

4. Link Building: How to Brief a Campaign Safely

Link building remains a high-risk, high-reward service. A poorly executed campaign can lead to a manual action or algorithmic penalty. When briefing an agency, insist on transparency and a white-hat approach.

Backlink Profile Analysis

Before any outreach begins, the agency should audit your existing backlink profile using tools like Ahrefs or Majestic. They should:

• Identify toxic backlinks (spam directories, paid link networks, irrelevant sites) and recommend disavowal if the volume is significant.
• Analyze your Domain Authority and Trust Flow. A site with high DA but low Trust Flow may have an unnatural link profile.
• Benchmark against competitors to identify realistic link acquisition targets.

Outreach and Content Strategy

A responsible link building campaign focuses on earning links through valuable content, not buying them. The agency should:

• Create linkable assets: original research, data visualizations, comprehensive guides, or interactive tools.
• Conduct outreach to relevant sites (industry blogs, news outlets, resource pages) with a personalized pitch.
• Track link acquisition with a clear reporting structure: target URL, referring domain, link type (dofollow/nofollow), and date acquired.

Checklist item: Ask for a sample outreach email. If the email reads like a template with generic flattery (“I love your site”), the campaign is likely low-quality. A good outreach email references a specific article on the target site and explains why your content adds value to their audience.

Risk callout: Avoid agencies that offer a fixed number of links per month at a flat rate. This model incentivizes quantity over quality and often leads to links from PBNs (private blog networks) or low-quality directories. A single link from a reputable, relevant site is worth more than fifty links from spam domains.

5. Reporting and Accountability

Finally, the agency’s reporting structure determines whether you can hold them accountable for results. Demand:

• A monthly report that covers organic traffic trends, keyword ranking movements, indexation changes, and Core Web Vitals scores.
• A separate technical health report that tracks crawl errors, broken links, and sitemap issues.
• A transparent breakdown of link building activity: links acquired, links lost, outreach metrics (response rate, conversion rate).

Checklist item: Verify that the agency uses your Google Search Console and Google Analytics accounts (with read-only access) rather than their own tracking tools. You should own the data.

Summary: Your Agency Briefing Checklist

Before you sign a contract, ask the agency to confirm they will:

1. Perform a log file analysis for crawl budget assessment.
2. Audit XML sitemap, robots.txt, and canonical tags.
3. Measure and report Core Web Vitals with a remediation plan.
4. Map keywords to pages by search intent.
5. Provide a content strategy that addresses thin content and cannibalization.
6. Conduct a backlink profile audit before starting link building.
7. Use content-based outreach, not paid links or PBNs.
8. Test performance improvements in a staging environment.
9. Report monthly with transparent, ownable data.

A thorough agency will welcome these requirements. A vendor that resists them or offers vague assurances is likely cutting corners. Use this checklist as your first line of defense.