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Where AI agents find a data service in 2026: MCP registries, x402 directories and ERC-8004

#mcp #ai #agents #web3

People find a website through search. AI agents mostly don't browse: they read registries, manifests and machine-readable files, then call what they find. If your service isn't in those places, agents never learn it exists, however good your pages are.

We build Agentic Finance Graph, an independent ledger of the money AI agents hold and spend on Base. Every ERC-8004 registration is joined to the wallet that spends for it, and every stablecoin payment is checked against its receipt. The figures are dated, every one has a definition, and they're free to read.

These are the places we listed it, what each one asks of you, and what we'd tell anyone doing the same.

1. MCP registries: where AI clients look for tools

Our MCP server is remote and stateless. It needs no key, and its 11 tools are all read-only:

https://agenticfinancegraph.com/mcp   (Streamable HTTP)
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In Claude Code:

claude mcp add --transport http afg https://agenticfinancegraph.com/mcp
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In Cursor, Windsurf or VS Code, add a remote MCP server with that URL. Clients that only speak stdio can run the open-source bridge: npx -y github:AgenticFinanceGraph/agentic-finance-graph-mcp mcp.

Where it is listed:

  • Official MCP Registry as com.agenticfinancegraph/agentic-finance-graph. The name is verified against our domain through /.well-known/mcp-registry-auth, an Ed25519 public key, so nobody else can publish under it.
  • Smithery, under our own namespace.
  • Glama. Glama indexes public GitHub repos by itself. When we tried to submit, it answered "already exists", so we claimed the existing page instead.

The tools: market_state, find_agent, agent_record, ranked_agents, detections, definition, metric_history, since_last, agent_statement, counterparty_preview and evidence_pack_quote. None of them can move funds.

2. x402 directories: where agents look for things to pay for

Most of the data is free. On top of it we sell nine evidence packs: dated, citable files about one agent or one address, priced from 1 to 25 cents in USDC on Base, paid over x402 with no account.

Without payment, a pack URL answers 402 Payment Required with the exact terms:

curl -i "https://agenticfinancegraph.com/check/liveness?id=53008"
# HTTP/1.1 402 Payment Required
# PAYMENT-REQUIRED: <base64: x402Version 2, amount 10000 (0.01 USDC), network eip155:8453>
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Where it is listed:

  • Coinbase's x402 Bazaar (the CDP discovery catalogue). All nine packs are listed. The Bazaar adds a resource only after a real payment has settled, so we bought each pack once ourselves.
  • x402scan, which registered all 37 of our paid resources from our OpenAPI file.
  • Our own manifest at /.well-known/x402.

One thing we learned the hard way: directories probe bare routes without parameters. A route that answers 400 instead of 402 looks broken to them. Ours answers 402 with the published terms even when no id is given.

3. An agent-readable website

  • llms.txt: what we measure, when to call us, which call is free, and which pack costs what.
  • openapi.json: every endpoint, including the paid ones.
  • /.well-known/agent-card.json: an A2A agent card.
  • robots.txt explicitly welcomes retrieval and answer-engine crawlers. Until September it blocked our own API from them, which left AI answers quoting stale prose instead of live figures.

4. An identity: ERC-8004

Agentic Finance Graph is itself registered as ERC-8004 agent #95875 on Base. If we track agents' identities and wallets, we should have one too.

5. Open source on GitHub

What we'd tell anyone listing a service for agents

  1. Verify your name. Domain-verified registry names stop impostors and cost one TXT record or one well-known file.
  2. Answer bare routes. Catalogues probe endpoints with no parameters. Give them a useful 402, never a confusing 400.
  3. Settle once. Some x402 catalogues list a resource only after a real payment. Budget a few cents to buy your own products.
  4. Keep a free path. Agents (and people) trust a paid pack more when the free record it packages is one call away.
  5. Date and define every number. Agents quote you. Give them an as_of and a definition id to quote with it.

Everything above is free to read under CC BY 4.0: agenticfinancegraph.com. The MCP server, the API and the spec are public. If you build agents that pay, tell us what you'd want to ask the ledger.

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