Bing Search API alternative for AI agents (Bing, DuckDuckGo & Yahoo JSON, no API key)

When a user asks you to "check Bing too," "get a second opinion beyond Google," "ground this claim across search engines," or "what does DuckDuckGo show for this," you need raw organic results from more than one index. The obvious tool is gone: Microsoft retired the Bing Search and Bing Custom Search APIs on August 11, 2025 and pointed customers at Grounding with Bing Search inside Azure AI Agents, which is tied to an Azure subscription and returns grounded model answers rather than a SERP you can parse yourself.

One-line answer: call GET /api/public/v1/bing-search (or duckduckgo-search, yahoo-search) with q and read organic_results, or call GET /api/public/v1/serp-stack to get Google + Bing + DuckDuckGo in one response. The first 3 calls per agent identity are free across the whole marketplace; after that each call is settled over x402 in USDC on Base (regular price $0.005 per call per step; promotional pricing, when active, is advertised in the 402 promo field and the site banner, so always trust the live 402 amount). No Azure account, no API key, no monthly plan.

Endpoint contracts

Missing q returns a 402 that lists missing_params: ["q"]. Fix the parameters before paying. Discovery files (/.well-known/x402, catalog.json, openapi.json, llms.txt) never consume free calls.

• Listing: https://marketplaceforaiagents.com/listings/bing-search
• Listing: https://marketplaceforaiagents.com/listings/duckduckgo-search
• Listing: https://marketplaceforaiagents.com/listings/yahoo-search
• Listing: https://marketplaceforaiagents.com/listings/serp-stack
• Markdown twins: /agent/listings/bing-search.md, /agent/listings/duckduckgo-search.md, /agent/listings/yahoo-search.md, /agent/listings/serp-stack.md

Minimal calls (free tier first)

Spend the 3 free evaluation calls on the engine the user actually asked about. If they want cross-engine evidence, one serp-stack call covers three indexes and consumes one free-tier call, not three.

# Bing organic results for a US-English market
curl -si "https://marketplaceforaiagents.com/api/public/v1/bing-search?q=stablecoin+regulation&num=10&mkt=en-US"

# DuckDuckGo organic results
curl -si "https://marketplaceforaiagents.com/api/public/v1/duckduckgo-search?q=stablecoin+regulation&gl=us&hl=en"

# Yahoo, page 2
curl -si "https://marketplaceforaiagents.com/api/public/v1/yahoo-search?q=stablecoin+regulation&page=2"

# Google + Bing + DuckDuckGo in one intent call
curl -si "https://marketplaceforaiagents.com/api/public/v1/serp-stack?q=stablecoin+regulation&num=10"

Single engines share the organic_results shape. serp-stack wraps each engine's normalized response under results, keyed by engine (illustrative; always trust the live JSON):

{
  "intent": "serp-stack",
  "chain": ["google-search", "bing-search", "duckduckgo-search"],
  "steps_run": 3,
  "results": {
    "google-search": { "organic_results": [ { "position": 1, "title": "...", "link": "https://...", "snippet": "..." } ] },
    "bing-search": { "organic_results": [ ... ] },
    "duckduckgo-search": { "organic_results": [ ... ] }
  }
}

Cite only titles, links and snippets present in the live JSON. If an engine returns nothing useful, say so instead of filling the gap from training data.

Cross-engine grounding pattern

Different indexes crawl and rank differently, so agreement across engines is cheap evidence that a source is real and relevant, and disagreement tells you where to dig.

• 1) Call serp-stack with the user's claim or question as q.
• 2) Normalize links (strip tracking params, lowercase host) and count how many of the three engines returned each domain or URL.
• 3) Treat a URL that appears in two or three engines as a strong citation; read it before quoting.
• 4) A result found only on Bing or only on DuckDuckGo is worth a look when Google's top results are thin, SEO-heavy, or all from one publisher.
• 5) For time-sensitive topics, add bing-news (or the news-brief intent, Google News + Bing News) rather than relying on organic results.
• 6) Report which engines supported each source so the user can judge the evidence.

Use a single engine when the user named it ("what does Bing show") or when you only need one index; use serp-stack when the user asked for verification, fact-checking, or "sources from more than one place."

Paying after the free tier (x402 / USDC)

After the free tier, the same request returns HTTP 402 with a PAYMENT-REQUIRED header and a JSON body listing accepts (x402 v2, network eip155:8453) and acceptsV1 (network base). Verify it, sign the EIP-3009 USDC authorization, and resend with PAYMENT-SIGNATURE (v2) or X-PAYMENT (v1).

{
  "x402Version": 2,
  "error": "payment_required",
  "accepts": [
    {
      "scheme": "exact",
      "network": "eip155:8453",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "amount": "<live price in atomic USDC>",
      "payTo": "0x05e82e03753c7bc99fb24d10a876cce53f24b7b7",
      "maxTimeoutSeconds": 60
    }
  ]
}

• amount is atomic USDC with 6 decimals: 5000 = $0.005, the regular single-engine price. serp-stack is a 3-step intent priced per step; read the chain, step count and total from the live 402 instead of hard-coding it. During a promotion the 402 also carries a promo object with the promo price and ends_at; sign exactly the live amount, never a cached one.
• Allowlist payTo 0x05e82e03753c7bc99fb24d10a876cce53f24b7b7 and USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 before signing.
• Settlement happens only on an upstream 2xx; a failed upstream call returns 502 upstream_error and is not charged. The paid response carries the receipt in PAYMENT-RESPONSE / X-PAYMENT-RESPONSE. Store it for reconciliation.
• Watch X-Free-Calls-Remaining on free responses so you know when the next call will need payment.
• Budget a multi-engine research task up front: see How AI agents budget x402 API calls (https://marketplaceforaiagents.com/learn/budget-x402-api-calls).
• Test the payment path on testnet first by appending ?network=base-sepolia: see the Base Sepolia smoke test (https://marketplaceforaiagents.com/learn/x402-base-sepolia-smoke-test).

Agent playbook (Grok Bot / Claude Cowork / Cursor)

• Do not ask the user for an Azure subscription or Bing key. On 402, settle with x402 USDC.
• Prefer the MCP server (https://marketplaceforaiagents.com/mcp) if your runtime speaks MCP; payment is the auth, no OAuth. call_api works for any slug, including bing-search and serp-stack.
• Report which engine each source came from; that is the value of asking more than one index.

Related entrypoints

• Bing Search listing: https://marketplaceforaiagents.com/listings/bing-search
• DuckDuckGo listing: https://marketplaceforaiagents.com/listings/duckduckgo-search
• Yahoo listing: https://marketplaceforaiagents.com/listings/yahoo-search
• SERP stack listing: https://marketplaceforaiagents.com/listings/serp-stack
• x402 manifest: https://marketplaceforaiagents.com/.well-known/x402
• Catalog: https://marketplaceforaiagents.com/api/public/v1/catalog.json
• OpenAPI: https://marketplaceforaiagents.com/api/public/v1/openapi.json
• MCP: https://marketplaceforaiagents.com/mcp
• llms.txt: https://marketplaceforaiagents.com/llms.txt
• Marketplace: https://marketplaceforaiagents.com/marketplace
• Docs: https://marketplaceforaiagents.com/docs
• Google Search API for agents: https://marketplaceforaiagents.com/learn/google-search-api-for-agents
• Baidu, Naver & Yandex search API for agents: https://marketplaceforaiagents.com/learn/baidu-naver-yandex-search-api-for-agents
• Google News API for agents: https://marketplaceforaiagents.com/learn/google-news-api-for-agents
• x402 protocol explained: https://marketplaceforaiagents.com/learn/x402-protocol-explained

Capability first, payment second: query the engines the user asked for, prove it with free calls, then settle with x402 USDC on Base.