pyATS MCP Server

Cisco pyATS and Genie already know how to talk to a network — parsing show commands, pushing configuration, learning feature state, running declarative tests. What they didn't have was a way for an AI agent to drive any of it directly. This server closes that gap: it wraps pyATS/Genie as a set of structured, guarded MCP tools that an agent like Claude can call against a real testbed, over the Model Context Protocol's current Streamable HTTP transport.

Point an agent at it and it can look up a device, run and parse a show command, apply configuration with a rollback point, learn and diff a feature's state before and after a change, fan a command out across a fleet — one thread pool or one process per device — run a declarative Blitz or Robot Framework test, or call a device's REST/RESTCONF API directly. Every risky path is guarded before it reaches a device, and every call lands in an in-memory audit log the agent can review mid-session.

At a glance

• Transport — Streamable HTTP (mcp>=2.0.0), stateful or stateless, chosen with one environment variable. STDIO is gone.
• 26 tools across discovery, show commands, configuration, Genie learn/diff, Genie Clean, declarative testing (Blitz, Robot Framework, AEtest), generic REST/RESTCONF, and Cisco XPresso.
• Two ways to fan out a command across many devices — a shared thread pool for everyday use, or one OS process per device (pyats.async_.pcall) when you want real isolation at scale.
• Guardrails, not honor systems — dangerous commands are blocked before they reach a device, Genie Clean can never run a stage that reboots or reimages one, and destructive actions require an exact confirmation phrase.
• Nothing hard-coded — every credential and device detail lives in .env, pulled into testbed.yaml at runtime via %ENV{} substitution.

Prerequisites

• Python 3.10+
• A pyATS testbed.yaml pointed at real or virtual network devices — a physical lab, Cisco Modeling Labs / VIRL / GNS3, or anything else Unicon can reach over SSH/Telnet. pyATS MCP doesn't simulate a network; it drives one.
• An MCP-capable client to talk to it — see Connect Your Agent below.

Quick Start

# 1. Clone and install
git clone https://github.com/automateyournetwork/pyATS_MCP
cd pyATS_MCP
pip install -r requirements.txt

# 2. Configure your environment
cp .env.example .env
# Edit .env — see Configuration below

# 3. Run — starts a Streamable HTTP server on 0.0.0.0:8080 by default
python3 pyats_mcp_server.py

The MCP endpoint is then reachable at http://<host>:<port>/mcp.

Configuration

All device details and credentials live in a .env file — nothing is hard-coded in the repo.

1. Copy the template

cp .env.example .env

2. Set the server variables

PYATS_TESTBED_PATH=/absolute/path/to/your/testbed.yaml
PYATS_MCP_ARTIFACTS_DIR=          # default: ~/.pyats-mcp/artifacts
PYATS_MCP_KEEP_ARTIFACTS=1        # 1 = keep, 0 = delete after each run
PYATS_MCP_TESTBED_CACHE_TTL=30    # seconds before testbed reloads from disk
PYATS_MCP_CONN_CACHE_TTL=0        # seconds to keep connections alive (0 = off)
PYATS_MCP_OP_LOG_MAX=500          # max entries in the in-memory operation log

# Transport (Streamable HTTP only — STDIO is not supported)
PYATS_MCP_TRANSPORT_MODE=stateful # stateful (default) | stateless
PYATS_MCP_HTTP_HOST=0.0.0.0
PYATS_MCP_HTTP_PORT=8080

# Optional — only needed for pyats_xpresso_request
XPRESSO_URL=
XPRESSO_API_TOKEN=
XPRESSO_GROUP=

PYATS_MCP_TRANSPORT_MODE=stateless sets stateless_http=True on the Streamable HTTP transport, so no server-side session state is retained between requests from clients still negotiating the older, handshake-based protocol. Clients speaking the current MCP protocol (2026-07-28, SEP-2575) are handshake-free by default regardless of this setting — that comes from the mcp>=2.0.0 SDK itself, not anything configured here.

3. Add a block for each device

Every device in your testbed.yaml uses %ENV{VAR} substitution, so credentials and connection details are read from .env at runtime.

Use the {DEVICENAME}_{FIELD} naming convention:

# Supported os values: iosxe | iosxr | nxos | ios | eos | junos | panos | linux | windows
# Set os=generic and platform="" to let Unicon autodetect on first connect.

CORE1_IP=10.1.1.1
CORE1_PORT=22
CORE1_OS=iosxe
CORE1_PLATFORM=cat9k
CORE1_USERNAME=admin
CORE1_PASSWORD=s3cr3t
CORE1_ENABLE_PASSWORD=s3cr3t

FW1_IP=10.1.1.2
FW1_PORT=22
FW1_OS=panos
FW1_PLATFORM=
FW1_USERNAME=admin
FW1_PASSWORD=s3cr3t
# (no enable password for Palo Alto)

LINUX1_IP=10.1.1.3
LINUX1_PORT=22
LINUX1_OS=linux
LINUX1_PLATFORM=ubuntu
LINUX1_USERNAME=admin
LINUX1_PASSWORD=s3cr3t
# (no enable password for Linux)

If a group of devices shares credentials, define group-level vars and reference them across devices:

SITE_A_USERNAME=netops
SITE_A_PASSWORD=s3cr3t
SITE_A_ENABLE_PASSWORD=s3cr3t

4. Reference the variables in testbed.yaml

devices:
  CORE1:
    alias: "Core Switch 1"
    type: "switch"
    os: "%ENV{CORE1_OS}"
    platform: "%ENV{CORE1_PLATFORM}"
    credentials:
      default:
        username: "%ENV{CORE1_USERNAME}"
        password: "%ENV{CORE1_PASSWORD}"
      enable:
        password: "%ENV{CORE1_ENABLE_PASSWORD}"
    connections:
      cli:
        protocol: ssh
        ip: "%ENV{CORE1_IP}"
        port: "%ENV{CORE1_PORT}"
        arguments:
          connection_timeout: 360

For devices with unknown OS, set os: "%ENV{DEVICE_OS}" with DEVICE_OS=generic in .env and optionally add learn_os: true under arguments: — Unicon will detect and cache the OS after the first connection.

Docker

Build

docker build -t pyats-mcp-server .

Run (pass .env directly)

docker run -p 8080:8080 --rm \
  --env-file /absolute/path/to/.env \
  -v /absolute/path/to/testbed.yaml:/app/testbed.yaml \
  pyats-mcp-server

Either way, the server is a long-running process you start once and point clients at — it isn't something an agent spawns per session. See below for exactly how each client connects to it.

Connect Your Agent

The server exposes one thing: an MCP endpoint at http://<host>:<port>/mcp (Streamable HTTP). Every client below just needs that URL — no command/args, no local process for the client to manage.

Claude Code

claude mcp add --transport http pyats http://localhost:8080/mcp

# Behind auth (e.g. a reverse proxy in front of the server)
claude mcp add --transport http pyats http://localhost:8080/mcp \
  --header "Authorization: Bearer your-token"

Or drop it straight into .mcp.json (project-scoped, committed to the repo) or ~/.claude.json (user-scoped):

{
  "mcpServers": {
    "pyats": { "type": "http", "url": "http://localhost:8080/mcp" }
  }
}

VS Code (GitHub Copilot Chat)

Add a .vscode/mcp.json in the workspace (or run MCP: Add Server from the Command Palette):

{
  "servers": {
    "pyats": { "type": "http", "url": "http://localhost:8080/mcp" }
  }
}

OpenAI Codex CLI

codex mcp add pyats --url http://localhost:8080/mcp

Or in ~/.codex/config.toml:

[mcp_servers.pyats]
url = "http://localhost:8080/mcp"

Claude Desktop

Claude Desktop's claude_desktop_config.json is stdio-only — putting a url field in it doesn't work (it's a known issue, not a supported path). Remote/HTTP servers are added instead as a Custom Connector under Settings → Connectors, and Desktop connects to it from Anthropic's cloud, not your local machine — so it needs a real, publicly-reachable HTTPS URL, not localhost.

To point Desktop at a server running on your own machine anyway, bridge it through mcp-remote as a local stdio proxy:

{
  "mcpServers": {
    "pyats": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "http://localhost:8080/mcp", "--transport", "http-only"]
    }
  }
}

Raw Python (LangGraph, custom agents, anything else)

from mcp import ClientSession
from mcp.client.streamable_http import streamablehttp_client

async def main():
    async with streamablehttp_client("http://localhost:8080/mcp") as (read, write, _session_id):
        async with ClientSession(read, write) as session:
            await session.initialize()
            tools = await session.list_tools()
            result = await session.call_tool(
                "pyats_run_show_command",
                arguments={"device_name": "CORE1", "command": "show version"},
            )

What To Ask It

Once connected, talk to it like you'd talk to someone who already knows the network:

• "What devices are in the testbed?" → pyats_list_devices
• "Show me the BGP summary on CORE1" → pyats_run_show_command, parsed into structured JSON
• "Snapshot CORE1's OSPF state, then apply this config and show me what changed" → pyats_learn_feature (before) → pyats_configure_with_diff → pyats_learn_feature (after) → pyats_diff_learned_snapshots
• "Run show ip interface brief across every switch" → pyats_run_show_command_multi (or pyats_pcall_show_command for process-per-device isolation at real scale)
• "If that config change breaks anything, roll it back" → pyats_rollback_config
• "Run this Blitz test against R1 and R2" / "Run this Robot Framework suite" → pyats_run_blitz / pyats_run_robot

The agent chains these itself — you describe the outcome, it picks the tools.

Available Tools

26 tools, grouped by what they do.

Discovery

Show commands

Configuration

State & diagnostics

Testing & automation

APIs

Session

Security

• Show commands are validated — pipes, redirects, and dangerous keywords are blocked.
• Config changes are checked for reload, erase, write erase, delete, format — the same check runs inside pyats_clean_device, pyats_run_blitz, and pyats_run_robot.
• Dynamic test scripts run in a restricted sandbox (banned imports: os, sys, subprocess, etc.).
• pyats_clean_device never runs a real Genie Clean stage that reboots, erases, or reimages a device — only connect+execute_command are ever generated — and defaults to dry_run=True; running for real also requires an exact confirmation phrase.
• Every process-global cache (connection cache, testbed cache, config/learn snapshots, operation log) is protected by a lock, so concurrent HTTP clients can't corrupt shared state.
• All credentials come from .env — never stored in the testbed file or source code.

Project Structure

.
├── pyats_mcp_server.py      # MCP server
├── test_pyats_mcp_server.py # Unit tests (119 tests)
├── benchmark/               # Pre/post, stateful/stateless transport benchmark
├── Dockerfile               # Container definition
├── requirements.txt         # Pinned runtime dependencies
├── requirements-dev.txt     # Dev/test dependencies
├── pyproject.toml           # Tool config (black, isort, pytest, mypy)
├── .env.example             # Configuration template — copy to .env
├── .gitignore
├── LICENSE
└── CONTRIBUTING.md

Development

# Install dev dependencies with uv
uv venv .venv && uv pip install -r requirements-dev.txt

# Run tests
.venv/bin/python -m pytest

# Lint and format
.venv/bin/black .
.venv/bin/isort .
.venv/bin/flake8 . --max-line-length=100

See CONTRIBUTING.md for the full setup and PR workflow.

Benchmark

benchmark/ compares STDIO (legacy) against Streamable HTTP in both stateful and stateless mode, against a real testbed. See benchmark/scenarios.py for the scenario list and benchmark/aggregate.py for building the comparison report; benchmark/results/summary.md has the most recent run's numbers.

License

MIT