Agentropolis examples: find and pay for agent tools with MCP + x402

Kits used in the examples:

Agentropolis is a free, no-auth search engine for agent tools: MCP servers, x402 and MPP pay-per-call APIs, A2A agents and "kits". Its trust scores come only from verified, non-wash on-chain payments.

Each example here does the same four things with a different agent framework:

1. Connects to the Agentropolis MCP server at https://agentropolis.io/api/mcp through the framework's own MCP adapter.
2. Calls search_kits to find tools for a task.
3. Calls get_kit_manifest to learn how to call the chosen kit: endpoint, sample input and x402 offer.
4. Pays the seller directly with x402, using your own wallet. The key comes from an env var.

Framework	File	MCP adapter	Payment
Vercel AI SDK (TypeScript)	typescript/src/vercel-ai-sdk.ts	@ai-sdk/mcp	@x402/fetch
Coinbase AgentKit (TypeScript)	typescript/src/coinbase-agentkit.ts	@ai-sdk/mcp (discovery)	AgentKit x402ActionProvider
LangChain (Python)	python/langchain_example.py	langchain-mcp-adapters	x402 (Python)
CrewAI (Python)	python/crewai_example.py	crewai-tools[mcp] MCPServerAdapter	x402 (Python)
OpenAI Agents SDK (Python)	python/openai_agents_example.py	agents.mcp.MCPServerStreamableHttp	x402 (Python)

Safety first

• No real keys in this repo, ever. Put BUYER_PRIVATE_KEY in .env, which is git-ignored. Use a dedicated hot wallet holding only a few dollars of USDC.
• Dry run by default. Without --pay, the examples only show the seller's 402 quote. Nothing is signed.
• Spend cap. Every payment goes through a client policy that refuses any requirement above MAX_PAYMENT_USD (default 0.05) or on another network than X402_NETWORK.
• Non-custodial. Agentropolis never holds keys or funds and never pays for you. You pay the seller's payTo, the seller's facilitator settles, and settlement happens only after a successful response.
• The LLM does not hold your wallet. The --agent mode lets a model use the read-only MCP tools to research. Payments stay in plain code behind the cap.

Quick start

git clone https://github.com/seenly721/agentropolis-examples && cd agentropolis-examples
cp .env.example .env            # add BUYER_PRIVATE_KEY only when you want to pay

# TypeScript (Node 20+)
cd typescript && npm install
npm run ai-sdk                  # search + manifest + 402 quote (no wallet needed)
npm run ai-sdk -- --free        # use a free daily call on a Seenly kit (no wallet needed)
npm run ai-sdk -- --pay         # pay $0.02 USDC on Base from YOUR wallet
npm run agentkit -- --pay       # same with Coinbase AgentKit's x402 actions
cd ..

# Python (3.10+)
python -m venv .venv && . .venv/bin/activate
pip install -r python/requirements.txt
cd python
python langchain_example.py [--free] [--pay] [--agent]
python crewai_example.py [--free] [--pay] [--agent]
python openai_agents_example.py [--free] [--pay] [--agent]

Sample output (dry run):

Connected to https://agentropolis.io/api/mcp: 10 tools (search_kits, get_kit, get_kit_manifest, call_kit, ...)

search_kits("token honeypot check on Base") -> 526 matches. Top results:
  - x402.token-safety-check-x402  $0.03  trust=54  Token Safety Check (x402)
  ...
  * featured (first-party): seenly.seenly-token-preflight  Token Preflight — Base pre-trade token check

get_kit_manifest(seenly.seenly-token-preflight) -> POST https://seenly-token-preflight.vercel.app/api/token-preflight

402 quote: 20000 base units (0.02 USDC) on eip155:8453 -> payTo 0xeE62…78CE. Bazaar metadata: yes

Dry run: add --pay to sign the payment with BUYER_PRIVATE_KEY.

--agent also runs an LLM loop over the same MCP tools. It needs a model key: OPENAI_API_KEY, or for the AI SDK, AI_GATEWAY_API_KEY.

Choosing what to buy

KIT_ID defaults to seenly.seenly-token-preflight, a $0.02 Base token safety check. Disclosure: it is a first-party kit by Seenly, which is affiliated with Agentropolis. Agentropolis labels first-party kits as "featured" and never mixes them into organic results.

To buy something else, set KIT_ID to any id from search_kits. Set KIT_INPUT_JSON if its manifest has no sample input. Always trust the seller's live 402 over any listed price.

Free daily allowance (Seenly kits)

Token Preflight, Transcript+ and Pitch Kit each give a few free calls per day. A request opts in with the header X-Free-Allowance: use; the --free flag sends it.

• Each caller network (IPv4 /24 or IPv6 /64) gets 3 free calls per UTC day on each kit.
• Each kit also has a global daily cap.
• Transcript+ free calls cover audio up to 2 minutes.

After that the same request returns the normal x402 402. Free calls are never counted as sales or trust. Details are in each kit's llms.txt and in https://agentropolis.io/llms.txt.

Testing without real money

Run any kit locally in test mode (Base Sepolia, x402.org facilitator) and point the examples at it:

export X402_NETWORK=eip155:84532 KIT_ENDPOINT_OVERRIDE=http://localhost:3412/api/token-preflight
export BUYER_PRIVATE_KEY=0x...   # a testnet wallet with Base Sepolia USDC (faucet.circle.com)
npm run ai-sdk -- --pay          # or any Python example with --pay

These examples were tested this way. Each of the five completed a Base Sepolia x402 payment, and the spend cap refused over-budget quotes. scripts/smoke.sh runs on every push and weekly. It does the connect/search/manifest/quote path against production and never pays.

Notes

• x402 v2: sellers answer with a PAYMENT-REQUIRED header. Clients retry with PAYMENT-SIGNATURE and get PAYMENT-RESPONSE, which carries the settlement tx hash. Payers need USDC only, no ETH.
• Bazaar: Seenly kits include Coinbase x402 Bazaar discovery metadata (extensions.bazaar) in their 402s.
• AgentKit telemetry: Coinbase AgentKit sends usage analytics to Coinbase, including the wallet address and action names. The example ignores failures of that call so they cannot crash your run.
• Relay: Agentropolis also offers a non-custodial relay (call_kit MCP tool, /api/v1/call/{id}) for listings marked buy: relay_x402. The examples pay sellers directly, which is simpler and does not depend on Agentropolis being up.

Links

• Install the MCP server in Cursor, VS Code or Claude Code: https://agentropolis.io/install
• Agent docs: https://agentropolis.io/llms.txt
• Badges and tiers: https://agentropolis.io/badges
• Contact: hello@agentropolis.io

MIT licensed. See LICENSE.