SpendFuel spendfuel.app

What Is SpendFuel? A Catalog of Paid Tools for AI Agents

· 2 min read

AI agents are starting to pay for things on their own: a search call here, a data lookup there, often a fraction of a cent at a time through the x402 payment protocol. Before an agent spends anything, it needs to find a tool that does the job, know what it costs and decide whether it is worth it. SpendFuel is being built to answer those questions.

What SpendFuel is today

SpendFuel is in its foundation phase. What works now:

  • A public catalog of paid and free APIs and MCP tools, with name, description, category, price in USD, pricing model, status and source. Browse it on the home page or query it as JSON.
  • Search and filters by free text, category, maximum price and verified status, sorted by rank, price, success rate or newest.
  • Budget-aware recommendations: give a goal and a budget and get a short list of candidate tools.
  • An MCP server at https://spendfuel.app/mcp with the live tools search_tools, recommend_tools and get_tool.
  • Automatic seeding. Every 12 hours a seeder pulls candidate endpoints from public x402 directories and curated lists, probes each one for an HTTP 402 payment challenge, and adds or updates it. Auto-seeded listings are marked unverified; claimed or verified listings are never overwritten by the seeder.

What is still coming

We would rather be clear about this than oversell it:

  • report_outcome (agents report whether a paid call worked) and get_spend_summary (wallet burn rate and budget) are listed as stubs. Rankings are meant to be driven by real paid outcomes once outcome reporting is live.
  • Ownership claims, so providers can verify their listings by DNS TXT record, a /.well-known/spendfuel-claim file or Cloudflare account proof, are on the roadmap.
  • Later phases cover wallet analytics, reputation, and a policy engine for teams.

Until outcome reporting launches, treat success rates and call counts in the catalog as listing data, not as independent measurements.

Who it is for

  • Agent builders who want their agent to find a paid tool by capability and price instead of hard-coding one.
  • People experimenting with x402 who want a quick view of which endpoints answer with a payment challenge.
  • Tool providers who want their paid API in front of agents.

Where it fits

SpendFuel is a Rewards Fuel project, alongside Rewards Fuel contests, RFWIN verifiable draws and RankFuel leaderboards. All of them are built to be used by AI agents as well as people.

Next: find x402 tools with the SpendFuel API, or connect your agent over MCP.

Keep reading