junos-mcp copilot-instructions.md

Repository overview

junos-mcp is an MCP (Model Context Protocol) server that exposes junos-ops (a Juniper JUNOS CLI tool/library) to AI assistants over stdio (default) or streamable-http transport. Built on the official mcp Python SDK's FastMCP (junos_mcp/server.py), with per-host NETCONF connection pooling in junos_mcp/pool.py.

See CLAUDE.md (Japanese) for the authoritative module/tool inventory and design notes — read it before reviewing changes to server.py or pool.py. Its tool/test counts have drifted upward before as tools were added, so don't treat those numbers in CLAUDE.md as exact — check grep -c '^@mcp.tool' junos_mcp/server.py and the test run output instead of citing a possibly-stale figure in review comments.

Build & validate

python3 -m venv .venv
. .venv/bin/activate
pip install -e ".[test]"
pytest tests/ -v

This mirrors .github/workflows/test.yml (matrix over Python 3.12–3.14 on Linux, plus one Windows 3.12 job specifically to guard against stdio newline regressions, modelcontextprotocol/python-sdk#2433), plus a lint job running ruff check . at a pinned version. ruff format is deliberately not gated (see ruff.toml) and there is no black/mypy job — don't hold diffs to a formatting or typing standard this repo hasn't opted into, and don't restate what ruff check already enforces.

What to focus review on in this repo

1. stdio transport: stdout is the JSON-RPC channel

server.py's module docstring documents the actual mechanism: junos-ops core functions (≥0.16.9) return structured dicts and never print; MCP tools render text via junos_ops.display.format_*(result), which return a string rather than printing one. No contextlib.redirect_stdout exists anywhere in the module — it isn't needed because nothing on this path calls print(). Flag any new tool code in server.py that calls print(), writes to stdout directly, or lets a dependency's default logging fall through to stdout.