Agent builders on X keep making the same point: reserve the maximum cost of a call _before_ it runs, and refuse the call once a cap is hit. Checking spend afterwards is just reporting. FastAF is built so that this works without guesswork. ## Why it works with FastAF * **The price is fixed per route and published up front.** Every route in [https://api.fastaf.co/openapi.json](https://api.fastaf.co/openapi.json) carries `x-payment-info.price` with `mode: "fixed"` and an exact USD amount. * **The 402 reply repeats the price before you pay.** An unpaid request returns HTTP 402 with `price.usd`, `asset: "USDC"` and `network: "eip155:8453"` (Base), plus the `PAYMENT-REQUIRED` header for x402 v2 clients. * **You are charged only on success.** The 402 body says: “Settled only if the request succeeds.” ## Price table (from the OpenAPI spec, 28 Oct 2026) Price per call Routes $0.003 serp, search, amazon, reddit $0.005 maps, youtube, scrape, news, scholar, jobs, linkedin\_jobs, patents, flights, bing, walmart, zillow, ebay, x, screenshot $0.010 shopping, ai, images $0.060 linkedin (public profiles) ## Pattern: reserve, call, release ``` import requests BUDGET_USD = 0.50 PRICES = {} # loaded once from the spec spec = requests.get("https://api.fastaf.co/openapi.json").json() for path, ops in spec["paths"].items(): info = ops.get("get", {}).get("x-payment-info", {}) if "price" in info: PRICES[path] = float(info["price"]["amount"]) spent = 0.0 def can_call(path): return spent + PRICES[path] <= BUDGET_USD def record(path, ok): global spent if ok: # FastAF settles only successful requests spent += PRICES[path] ``` 1. Before each call, check `spent + price <= budget`. If not, stop and return your own 402/“budget exhausted” to the agent. 2. Optionally make the unpaid request first and read `price.usd` from the 402 body as a live check. 3. Pay with your x402 client only when the reserve fits. ## Prefer a key instead? The same 402 body offers an account path: 500 free credits every month after verifying your email at [https://fastaf.co/signup/](https://fastaf.co/signup/), then optional prepaid credits. Related: [x402 scraping API, pay per call](/x402-scraping-api/) · [Google SERP API](/apis/google-serp-api/) · [Why agent retries cost more than you think](/how-to/agent-tool-retry-cost/) ## Reference * [x402 documentation](/docs/#x402): every parameter and response field * [Docs](/docs/): authentication, errors, MCP and [x402](/docs/#x402) * [Pricing](/pricing/): credit packs from $10, without expiry ## Other sources * [How to read public Amazon data when your requests fail](/how-to/read-amazon-data/) * [How to read public Google Search data when your requests fail](/how-to/read-google-data/) * [How to read public Walmart data when your requests fail](/how-to/read-walmart-data/) * [How to read LinkedIn data with an API](/how-to/read-linkedin-data/) * [How to read public eBay data when your requests fail](/how-to/read-ebay-data/) * [How to read public Booking.com data when your requests fail](/how-to/read-booking-data/) * [How to read X profile data with an API](/how-to/read-x-data/) * [How to read public Zillow data when your requests fail](/how-to/read-zillow-data/) * [Pay-per-call web scraping for AI agents with x402](/how-to/x402-pay-per-call-web-scraping/) * [MCP servers for Amazon, SERP and web scraping](/how-to/best-mcp-servers-amazon-serp-scraping/) * [Cost per agent: monthly SaaS vs x402 pay-per-call](/how-to/cost-per-agent-saas-vs-x402/) * [How FastAF handles heavy pages and timeouts](/how-to/heavy-pages-timeouts/) * [x402 endpoint discovery checklist: how agents find a paid API (and how FastAF passes it)](/how-to/x402-discovery-checklist/) * [Add FastAF to Claude Code, Codex and Cursor](/how-to/add-fastaf-claude-code-codex-cursor/) * [How to detect poisoned or incomplete SERP results in AI agents](/how-to/detect-poisoned-incomplete-serp-results/) * [Use FastAF from the Cloudflare Agents SDK](/how-to/fastaf-cloudflare-agents-sdk/) * [FastAF as a fallback search provider](/how-to/search-api-fallback-provider/) * [Budget a scraping job before you run it](/how-to/budget-scraping-job-fixed-prices/) * [Try FastAF for free, no card](/how-to/free-search-api-for-agents/) * [Too many MCP tools? Keep agent context small](/how-to/mcp-tool-schema-bloat/) * [How agents find an API (and where FastAF is)](/how-to/agent-discovery-files/) * [Why agent retries cost more than you think](/how-to/agent-tool-retry-cost/) * [All how-to guides](/how-to/) ## Compare * [FastAF vs SerpApi](/compare/serpapi/) * [FastAF vs Exa](/compare/exa/) * [FastAF vs Tavily](/compare/tavily/) * [FastAF vs Firecrawl](/compare/firecrawl/) * [FastAF vs Apify](/compare/apify/) * [FastAF vs toll402](/compare/toll402/) * [FastAF vs serp402](/compare/serp402/) * [FastAF vs AgentBIT](/compare/agentbit/) * [FastAF vs Amazon PA-API](/compare/amazon-pa-api/) * [FastAF vs Serper](/compare/serper/) * [FastAF vs ScrapingBee](/compare/scrapingbee/) * [FastAF vs ScraperAPI](/vs/scraperapi/) * [FastAF vs Bright Data](/vs/bright-data/) * [Benchmarks](/benchmarks/): latency and cost per 1,000 requests, measured ## Try it on your own request 500 free credits every month after email verification, no card. [Start free](/signup/)[x402 documentation](/docs/#x402) ## Related * [How to read public Amazon data when your requests fail](/how-to/read-amazon-data/) * [How to read public Google Search data when your requests fail](/how-to/read-google-data/) * [How to read public Walmart data when your requests fail](/how-to/read-walmart-data/)