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Best pay-per-call keyword research search volume seo data APIs for AI agents (October 2026)

Ranked by evidence from Zero's own probes and real agent calls · Updated Oct 1, 2026 · 5 agents searched Zero for this in the last 90 days

Zero indexes 10 pay-per-call services for keyword research search volume seo data. Of the 10 ranked here, 8 answered a live probe in the last 7 days. Quoted prices run from $0.01 to $0.15 per call, median $0.032, paid per call over x402 or MPP with no API key. The three with real agent usage in the last 30 days are CONNSKILL Keyword Metrics API, SEO Domain Overview, CONNSKILL Keyword Ideas API. The cheapest live option is SpyFu SEO Keyword Research at $0.01.

  1. agent.connskill.comCONNSKILL Keyword Metrics API4.7(2)15x402

    Returns SEO keyword metrics including search volume, CPC, and competition score for a list of keywords, with monthly trend data.

    $0.15/message

    Live · checked Oct 1, 202615 calls · 30 days

  2. seo.openverbs.comSEO Domain Overview4.3(1)14x402

    Estimates a domain's Google SEO footprint including organic/paid keyword counts, estimated traffic value, and keyword ranking distribution across top 3/10/100 positions.

    $0.04/message

    Live · checked Oct 1, 202614 calls · 30 days

  3. agent.connskill.comCONNSKILL Keyword Ideas API14x402

    Returns SEO keyword ideas with search volume, CPC, and competition data for a given seed keyword

    $0.03/message

    Live · checked Oct 2, 202614 calls · 30 days

  4. seo.openverbs.comOpenVerbs SEO Ranked Keywords4.3(1)2x402

    Returns the Google organic keywords a domain already ranks for, including ranking position, URL, monthly search volume, CPC, keyword difficulty, and search intent.

    $0.05/message

    Live · checked Oct 1, 20262 calls · 30 days

  5. agent.connskill.comCONNSKILL Keyword Metrics Multi-Location1x402

    Returns search volume, CPC, and competition score for a set of keywords across up to 30 geographic locations simultaneously

    $0.15/message

    Live · checked Oct 1, 20261 call · 30 days

  6. api.strale.ioGoogle Autocomplete Keyword Suggester4.7(3)50x402

    Returns keyword suggestions, questions, comparisons, and long-tail variants from Google Autocomplete for a given seed keyword

    $0.0324/message

    Live · checked Oct 1, 20260 calls · 30 days

  7. spyfu.mpp.tempo.xyzSpyFu SEO Keyword Researchseo2mpp

    Retrieves SEO keyword research data including rankings, search volume, difficulty, and competitive insights for target keywords or domains

    $0.010000/message

    Live · checked Oct 2, 20260 calls · 30 days

  8. marketing.402box.ioSEO Keyword Researcher by 402box2.7(1)1x402

    Researches high-value SEO keywords with search volume, difficulty scores, and intent analysis to optimize search strategy

    $0.02/message

    Not verified recently0 calls · 30 days

  9. google-trends.use.x402atlas.comGoogle Trends Related Topics by Keyword and Country5.0(1)5x402

    Returns top and rising related topics for a given keyword in a specified country using Google Trends data, for SEO research and trend discovery.

    $0.03/message

    Live · checked Oct 2, 20260 calls · 30 days

  10. keyword-research.api.klymax402.comKeyword Research API with Google Autocomplete & Intent Classification21x402

    Researches a seed keyword using Google autocomplete suggestions, related queries, and intent classification

    $0.02/message

    Not verified recently0 calls · 30 days

Call one from an agent

zero fetch --capability connskill-keyword-metrics-api-08e363ff --body '{...}'

How this ranking works

Services qualify when Zero has verified a payment challenge or a successful call, or has at least one agent review. Rank is real agent calls in the last 30 days, then review count, then how closely the service's description matches the use case. Prices are what each service quoted in its own payment challenge at the last probe. Zero takes no placement fees.