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feat(skills): add marktguru supermarket offer and price comparison skill

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Introduce the marktguru agent skill and MCP integration for searching supermarket deals, comparing product prices, and querying supported retail chains:
- Add Marktguru API client and MCP server script
- Add skill definition (SKILL.md) and supported supermarkets reference
- Add test suite covering Marktguru API integration and offer queries
This commit is contained in:
Moritz Graf
2026-10-05 21:20:16 +02:00
parent c3c7a4c8cf
commit 9d890a290f
7 changed files with 1312 additions and 0 deletions
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.agents/skills/marktguru/scripts/marktguru_mcp.py
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#!/usr/bin/env python3
"""
Marktguru MCP (Model Context Protocol) Server (Production Grade)
Exposes German supermarket flyers, discounts, and price comparison tools over standard JSON-RPC 2.0 stdio.
Key Design Principles:
- Zero external dependencies: Uses standard library only.
- Strict Protocol Compliance: Conforms to MCP (2024-11-05) and JSON-RPC 2.0 specifications.
- Defensive Argument Coercion: Tolerates string/number variations commonly output by LLMs.
- Graceful Signal Handling: Clean exit on SIGINT, SIGTERM, and EOF.
- Stream Isolation: All logs and diagnostics route to stderr, ensuring stdout is 100% clean JSON-RPC.
"""
import sys
import json
import signal
import logging
from typing import Dict, Any, List, Optional
# Import business logic from hardened client script
from marktguru_client import (
search_offers,
compare_prices,
list_supported_supermarkets,
DEFAULT_ZIP_CODE,
MAJOR_RETAILERS,
RETAILER_ALIASES,
)
# Configure logging strictly to stderr
logging.basicConfig(
stream=sys.stderr,
level=logging.INFO,
format="%(asctime)s [%(levelname)s] %(name)s: %(message)s"
)
logger = logging.getLogger("marktguru-mcp")
PROTOCOL_VERSION = "2024-11-05"
SERVER_NAME = "marktguru-mcp-server"
SERVER_VERSION = "1.1.0"
TOOLS = [
{
"name": "search_supermarket_offers",
"description": (
"Search current weekly supermarket offers and promotional discounts in Germany via the Marktguru API. "
"Supports filtering by postal code (PLZ) and specific supermarket chains (e.g. Aldi Süd, Aldi Nord, Lidl, Edeka, Rewe, Kaufland, Penny, Netto)."
),
"inputSchema": {
"type": "object",
"properties": {
"query": {
"type": "string",
"description": "The product or keyword to search for (e.g. 'Butter', 'Kaffee', 'Bier', 'Milch', 'Nutella', 'Schokolade')."
},
"zip_code": {
"type": "string",
"description": f"5-digit German postal code (PLZ). Defaults to '{DEFAULT_ZIP_CODE}' (Regensburg)."
},
"supermarkets": {
"type": "array",
"items": {"type": "string"},
"description": "Optional list of supermarket names to filter by (e.g. ['Aldi', 'Lidl', 'Edeka', 'Rewe', 'Kaufland', 'Penny', 'Netto', 'dm', 'Rossmann']). If omitted, all available retailers are included."
},
"limit": {
"type": "integer",
"description": "Maximum number of offers to return (default: 20, max: 50)."
}
},
"required": ["query"]
}
},
{
"name": "compare_supermarket_prices",
"description": (
"Compare current prices for a product across German supermarkets in a given postal code. "
"Returns results sorted from lowest to highest price, highlighting the cheapest deal, regular prices (UVP), and required loyalty app memberships."
),
"inputSchema": {
"type": "object",
"properties": {
"query": {
"type": "string",
"description": "The product or grocery item to compare (e.g. 'Kaffee', 'Butter', 'Bier', 'Olivenöl')."
},
"zip_code": {
"type": "string",
"description": f"5-digit German postal code (PLZ). Defaults to '{DEFAULT_ZIP_CODE}' (Regensburg)."
},
"supermarkets": {
"type": "array",
"items": {"type": "string"},
"description": "Optional list of supermarket names to compare (e.g. ['Aldi', 'Lidl', 'Edeka', 'Rewe'])."
}
},
"required": ["query"]
}
},
{
"name": "list_supported_supermarkets",
"description": (
"List all supermarket, discounter, hypermarket, and drugstore chains supported by the Marktguru service in Germany, "
"including their categories (Discounter, Supermarkt, Großfläche, Drogerie) and accepted name aliases."
),
"inputSchema": {
"type": "object",
"properties": {}
}
}
]
def _sanitize_supermarkets(sm_input: Any) -> Optional[List[str]]:
"""Coerces various LLM input formats (list, comma-string, single string) into a clean list."""
if not sm_input:
return None
if isinstance(sm_input, list):
return [str(s).strip() for s in sm_input if str(s).strip()]
if isinstance(sm_input, str):
return [s.strip() for s in sm_input.split(",") if s.strip()]
return None
def handle_initialize(req_id: Any, params: Dict[str, Any]) -> Dict[str, Any]:
return {
"jsonrpc": "2.0",
"id": req_id,
"result": {
"protocolVersion": PROTOCOL_VERSION,
"capabilities": {
"tools": {
"listChanged": False
}
},
"serverInfo": {
"name": SERVER_NAME,
"version": SERVER_VERSION
}
}
}
def handle_tools_list(req_id: Any) -> Dict[str, Any]:
return {
"jsonrpc": "2.0",
"id": req_id,
"result": {
"tools": TOOLS
}
}
def handle_tools_call(req_id: Any, params: Dict[str, Any]) -> Dict[str, Any]:
tool_name = params.get("name")
args = params.get("arguments", {})
logger.info(f"Tool call requested: {tool_name} with args={args}")
try:
if tool_name == "search_supermarket_offers":
query = str(args.get("query") or "").strip()
if not query:
return {
"jsonrpc": "2.0",
"id": req_id,
"result": {
"content": [{"type": "text", "text": "Error: 'query' argument is required and cannot be empty."}],
"isError": True
}
}
zip_code = str(args.get("zip_code") or DEFAULT_ZIP_CODE).strip()
supermarkets = _sanitize_supermarkets(args.get("supermarkets"))
try:
limit = int(args.get("limit") or 20)
except (ValueError, TypeError):
limit = 20
data = search_offers(query, zip_code=zip_code, supermarkets=supermarkets, limit=limit)
text_result = json.dumps(data, indent=2, ensure_ascii=False)
elif tool_name == "compare_supermarket_prices":
query = str(args.get("query") or "").strip()
if not query:
return {
"jsonrpc": "2.0",
"id": req_id,
"result": {
"content": [{"type": "text", "text": "Error: 'query' argument is required and cannot be empty."}],
"isError": True
}
}
zip_code = str(args.get("zip_code") or DEFAULT_ZIP_CODE).strip()
supermarkets = _sanitize_supermarkets(args.get("supermarkets"))
data = compare_prices(query, zip_code=zip_code, supermarkets=supermarkets)
text_result = json.dumps(data, indent=2, ensure_ascii=False)
elif tool_name == "list_supported_supermarkets":
data = list_supported_supermarkets()
text_result = json.dumps(data, indent=2, ensure_ascii=False)
else:
return {
"jsonrpc": "2.0",
"id": req_id,
"error": {
"code": -32601,
"message": f"Method or tool '{tool_name}' not found."
}
}
return {
"jsonrpc": "2.0",
"id": req_id,
"result": {
"content": [
{
"type": "text",
"text": text_result
}
],
"isError": False
}
}
except Exception as e:
logger.exception(f"Exception during tool execution '{tool_name}': {e}")
return {
"jsonrpc": "2.0",
"id": req_id,
"result": {
"content": [
{
"type": "text",
"text": f"Tool execution failed: {type(e).__name__}: {str(e)}"
}
],
"isError": True
}
}
def process_message(line: str) -> Optional[Dict[str, Any]]:
if not line.strip():
return None
try:
msg = json.loads(line)
except json.JSONDecodeError as e:
logger.error(f"Malformed JSON-RPC received: {e}")
return {
"jsonrpc": "2.0",
"id": None,
"error": {"code": -32700, "message": f"Parse error: {str(e)}"}
}
method = msg.get("method")
req_id = msg.get("id")
params = msg.get("params", {})
# Notifications do not return a response
if req_id is None:
if method == "notifications/initialized":
logger.info("Client acknowledged initialized notification.")
elif method == "notifications/cancelled":
logger.info(f"Client cancelled operation: {params}")
return None
# Standard Requests
if method == "initialize":
return handle_initialize(req_id, params)
elif method == "tools/list":
return handle_tools_list(req_id)
elif method == "tools/call":
return handle_tools_call(req_id, params)
elif method == "ping":
return {"jsonrpc": "2.0", "id": req_id, "result": {}}
else:
return {
"jsonrpc": "2.0",
"id": req_id,
"error": {
"code": -32601,
"message": f"Method '{method}' is not supported."
}
}
def _sig_handler(sig, frame):
logger.info(f"Received termination signal {sig}. Exiting gracefully.")
sys.exit(0)
def main():
signal.signal(signal.SIGINT, _sig_handler)
signal.signal(signal.SIGTERM, _sig_handler)
logger.info(f"Starting {SERVER_NAME} v{SERVER_VERSION} (stdio mode)...")
try:
for raw_line in sys.stdin:
response = process_message(raw_line)
if response is not None:
output = json.dumps(response, ensure_ascii=False) + "\n"
sys.stdout.write(output)
sys.stdout.flush()
except (KeyboardInterrupt, BrokenPipeError):
pass
except Exception as e:
logger.exception(f"Fatal error in stdio loop: {e}")
sys.exit(1)
logger.info("Marktguru MCP server shutdown complete.")
if __name__ == "__main__":
main()