# Lordevo tools for LangChain (Python)

> Needs `lordevo-x402` **0.1.5 or later** (on npm and PyPI; 0.1.3 has the LangChain tools but not `trial=True`).

Five web tools for a LangChain agent, paid per call with x402 (USDC on Base). No account and no API key. The tools come from the `lordevo_x402.langchain` module that ships inside the package; this folder adds the curated tool list and a runnable example.

| Tool | What it does | Price per call |
|---|---|---|
| `page_markdown` | A web page as clean, LLM-ready Markdown | $0.002 |
| `can_fetch` | robots.txt + AI-crawler permission check for a URL | $0.002 |
| `tech_stack` | What a site is built with (CMS, frameworks, analytics) | $0.002 |
| `dns_lookup` | DNS records (A, AAAA, CNAME, MX, TXT, NS, SOA, CAA) | $0.002 |
| `email_validate` | Email syntax + domain + MX (no mailbox probing) | $0.002 |

Prices are from the shop's price table (checked 13 Nov 2026; the published `lordevo-x402` 0.1.5 lists the same prices). The live price is always the one in the HTTP 402 and in https://shop.lordevo.com/catalog.json.

## Install
```bash
pip install "lordevo-x402[pay,langchain]>=0.1.5" langchain
```
`pay` brings `x402[httpx,requests,evm]` and `eth-account`; the EVM signer also needs `web3`, which `x402[evm]` installs. Without `pay`, only free trial calls work.

## Use (5 lines)
```python
import os
from langchain.agents import create_agent
from lordevo_x402 import LordevoSync
from lordevo_x402.langchain import langchain_tools
tools = langchain_tools(sync_client=LordevoSync.from_private_key(os.environ["AGENT_WALLET_KEY"], trial=True, max_price_usd=0.01), only=["page-markdown", "can-fetch", "tech-stack", "dns-lookup", "email-validate"])
agent = create_agent(os.environ["LANGCHAIN_MODEL"], tools=tools)
```
Then `agent.invoke({"messages": [{"role": "user", "content": "Read https://example.com and summarise it."}]})`. Leave out `only=` to get all tools.

## Free trial
With `trial=True` the first calls of the day are free: 3 calls per IP per UTC day on tools priced up to $0.005 (all five tools here). After that the client pays. Without a wallet key, use `LordevoSync(trial=True)`: free calls only; when they are used up a call raises `LordevoError` (status 402, `.used_up_today`), which LangChain's agent hands back to the model as the tool error.

## How payment works
An unpaid request gets HTTP 402 with the price. The x402 requests session signs a USDC payment from your agent wallet on Base and retries; the shop's facilitator settles it, so the wallet needs USDC but no ETH for gas. `max_price_usd` refuses any tool priced above it before a request is made. Answers of 400 or higher are not charged. Use a separate agent wallet with a small balance; key in an environment variable, never in code. `from_private_key` pays on Base mainnet (`eip155:8453`) only.

## Run the example
```bash
python example.py                              # free trial calls only
AGENT_WALLET_KEY=0x... python example.py       # free first, then paid
```
It invokes each tool once without an LLM, plus one bad input, and prints what happened. `make_client()` in the example is `from_private_key` written out, so the network can be set for a test copy of the shop (`LORDEVO_X402_NETWORK`).

MIT licence, like `lordevo-x402`. LangChain is MIT-licensed; only its public `StructuredTool` API is used.

## Files
- [example.py](https://shop.lordevo.com/guides/sdk/langchain-python/example.py)

All SDK guides: https://shop.lordevo.com/guides/sdk