LangChain Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory assay_get_ledger_policy
How to: LangChain Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory assay_get_ledger_policy
Add Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory to LangChain
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01
Open pip install langchain-mcp-adapters and merge this in. Keep any servers already there.
from langchain_mcp_adapters.client import MultiServerMCPClient
client = MultiServerMCPClient({
"assay": {
"transport": "streamable_http",
"url": "https://assay.agentdiet.dev/mcp",
}
})
tools = await client.get_tools()
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02
Save the file and restart LangChain.
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03
Ask for something assay_get_ledger_policy does. LangChain lists the server's tools on connect and calls assay_get_ledger_policy itself — you do not invoke it by name.
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04
If nothing happens, check the server is running and that Assay A2A, MCP & x402 Pre-Flight Verifier & Observatory's identifier in your config matches the one above exactly.
get_tools() returns the server's tools as LangChain tools, ready for an agent. LangChain docs
Same tool, other clients
This list was read from the server itself, by connecting to it and calling tools/list on 19 October 2026. It is what
the server actually exposes, not what its listing claims.
Mutating and Read-only are read off each tool's name, not its schema — a hint, not a guarantee. The registry stores tool names only; connect the server for its live schemas.