nodus-mcp 0.1.0

MCP (Model Context Protocol) library for Nodus — bidirectional client + server

nodus-mcp

Model Context Protocol (MCP) library for Nodus — bidirectional client and server, implementing the 2026-07-28 RC specification.

Status: v0.1.0 prepared, not yet published. Waiting for the coordinated launch with nodus-lang 4.0.0 and nodus-a2a v0.1.0. Two of three artifacts are ready.

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Authentication warning

v0.1 does not support OAuth 2.0. Only bearer-token authentication is implemented. Servers that require OAuth 2.0 / OIDC authentication (including many production MCP deployments) cannot be used with nodus-mcp v0.1. OAuth support is planned for v0.2.

To connect to a server with a bearer token:

from nodus_mcp import HttpTransport, McpClient

client = McpClient()
transport = HttpTransport("https://server/mcp", bearer_token="sk-...")
conn = client.connect(transport, alias="srv")

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Installation

# Once nodus-lang 4.0.0 is on PyPI:
pip install nodus-mcp

# Development install (both repos checked out):
pip install -e . --no-deps
# Set PYTHONPATH to nodus-lang source:
# PYTHONPATH="path/to/nodus-lang/src" python ...

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Quick start

Run an MCP server

# Spawned-child stdio mode (parent process connects to our stdin/stdout)
nodus-mcp serve --stdio

# HTTP mode
nodus-mcp serve --http --port 8080 --bearer-token my-api-key

To expose tools, use the Python API before serving:

from nodus_mcp import McpServer, HttpServerTransport

server = McpServer()
server.set_resource_list_handler(lambda: [
    {"uri": "file:///data", "name": "Data Directory"}
])

transport = HttpServerTransport("localhost", 8080)
transport.serve(server.dispatch)

Connect to a server

nodus-mcp connect http://localhost:8080 --bearer-token my-api-key

Interactive REPL:

Connected. Server: my-server 1.0. Tools: 3. Type 'help' for commands.
mcp> list
  my.tool — Does something useful
mcp> call my.tool {"x": 42}
{"content": [{"type": "text", "text": "done"}]}
mcp> quit

Use from a Nodus script

import "nodus-mcp"

// Discover and call tools (requires McpClient.connect() in host Python code)
let result = tool.invoke("mcp.srv.my_tool", {x: 42})

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Entry-point contract

# nodus-mcp registers itself in the nodus.nd entry-point group:
# nodus-mcp = "nodus_mcp.nd:get_nd_root"
#
# After pip install nodus-mcp, any Nodus script can:
#   import "nodus-mcp"
# and get the adapter module without additional configuration.
# See docs/guide/library-entry-points.md in nodus-lang for the contract.

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Deprecated features (Roots + Sampling)

nodus-mcp v0.1 includes Roots and Sampling despite their deprecation in the 2026-07-28 RC, because existing MCP servers in the ecosystem use them (real interop need) and the RC's 12-month deprecation window extends to at least 2027-07-28.

Do not remove Roots or Sampling before:

1. The protocol has actually removed them, AND
2. nodus-mcp has shipped a replacement

The removal gate is 2027-07-28 at the earliest. See docs/governance/TECH_DEBT.md (TD-001, TD-002) and docs/design/05-deprecated-features.md §C1.

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Known limitations

Limitation	Details
No OAuth support	Bearer token only; see auth warning above
resources/subscribe not implemented	Server-push deferred to v0.2
Server-initiated requests (HTTP)	roots/list, sampling/createMessage, elicitation/create are stdio-only; HTTP has no push channel (TD-007)
Partial JSON Schema validation	_validate_args checks required fields and primitive types; enum, pattern, minLength etc. are not enforced server-side (TD-008)
Resource handler KeyError convention	Resource read handlers must raise KeyError(uri) for unknown URIs (TD-009)
requestState is on the wire	Server-issued elicitation state travels to the client; never checkpoint secrets (TD-010)

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Spec target

2026-07-28 RC — stateless (no session initialization handshake, no Mcp-Session-Id). Capabilities travel in _meta per-request. server/discover replaces capability exchange.