First Version
This commit is contained in:
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#!/usr/bin/env python3
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"""SerpAPI Google Flights MCP server (JSON-RPC 2.0 over stdio).
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Capabilities:
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serpapi_search_flights — search one-way or round-trip flights via Google Flights
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through SerpAPI, returning prices, airlines, durations,
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layovers, and CO2 emissions.
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Auth:
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API key is read from env var SERPAPI_API_KEY, or from the file at
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SERPAPI_API_KEY_FILE (default: ./secrets/serpapi_api_key.txt).
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Run with:
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python3 scripts/mcp/serpapi_flights/server.py
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"""
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from __future__ import annotations
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import json
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import os
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import re
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import sys
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from typing import Any
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import httpx
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# Log to stderr so stdout stays clean for JSON-RPC.
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def log(msg: str) -> None:
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print(f"[serpapi_flights_mcp] {msg}", file=sys.stderr, flush=True)
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# ── API key / client init ──────────────────────────────────────────────────────
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SERPAPI_BASE_URL = "https://serpapi.com"
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_DEFAULT_KEY_FILE = os.path.join(
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os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))),
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"secrets",
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"serpapi_api_key.txt",
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)
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_init_error: str | None = None
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def _get_api_key() -> str | None:
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# 1. Environment variable
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key = os.environ.get("SERPAPI_API_KEY", "").strip()
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if key:
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return key
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# 2. File
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key_file = os.environ.get("SERPAPI_API_KEY_FILE", _DEFAULT_KEY_FILE)
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if os.path.exists(key_file):
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try:
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with open(key_file) as f:
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key = f.read().strip()
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if key:
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return key
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except OSError as e:
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global _init_error
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_init_error = f"Failed to read API key file {key_file}: {e}"
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log(_init_error)
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return None
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_init_error = (
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"SerpAPI API key not found. "
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"Set SERPAPI_API_KEY env var or create secrets/serpapi_api_key.txt "
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"with just the key on the first line."
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)
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log(_init_error)
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return None
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def _serpapi_request(params: dict) -> dict:
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"""Make a synchronous GET to SerpAPI /search. Raises on HTTP errors."""
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api_key = _get_api_key()
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if not api_key:
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raise _InitError(_init_error or "SerpAPI API key not configured.")
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full_params = {"api_key": api_key, **params}
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with httpx.Client(timeout=30.0, headers={"User-Agent": "skald-serpapi-mcp/2.0"}) as client:
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response = client.get(f"{SERPAPI_BASE_URL}/search", params=full_params)
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response.raise_for_status()
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return response.json()
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class _InitError(Exception):
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"""Raised when the API key is missing or unreadable."""
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# ── Error mapping ──────────────────────────────────────────────────────────────
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def _format_api_error(e: Exception) -> str:
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if isinstance(e, _InitError):
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return f"Error: {e}"
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if isinstance(e, httpx.HTTPStatusError):
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status = e.response.status_code
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if status == 401:
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return "Error: Invalid SerpAPI API key. Check secrets/serpapi_api_key.txt or the SERPAPI_API_KEY env var."
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if status == 429:
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return "Error: SerpAPI rate limit exceeded. Wait a moment and retry."
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if status == 400:
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return f"Error: Bad request — {e.response.text[:200]}. Verify airport codes (3-letter IATA) and dates."
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return f"Error: SerpAPI request failed (HTTP {status})."
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if isinstance(e, httpx.TimeoutException):
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return "Error: Request to SerpAPI timed out (30s). The service may be slow or unreachable; retry."
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if isinstance(e, httpx.RequestError):
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return f"Error: Network error contacting SerpAPI: {e}"
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return f"Error: Unexpected error: {type(e).__name__}: {e}"
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# ── Output formatting ──────────────────────────────────────────────────────────
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def _format_flight_results(data: dict, max_results: int) -> str:
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"""Render SerpAPI Google Flights results as plain text for the LLM."""
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best_flights = data.get("best_flights", []) or []
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other_flights = data.get("other_flights", []) or []
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price_insights = data.get("price_insights") or {}
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if not best_flights and not other_flights:
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return "No flights found for the given route and dates."
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lines: list[str] = []
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if price_insights:
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pi = price_insights
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if pi.get("lowest_price"):
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lines.append(f"Lowest price: {pi['lowest_price']}")
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if pi.get("typical_price_range"):
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lo, hi = pi["typical_price_range"][0], pi["typical_price_range"][1]
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lines.append(f"Typical range: {lo} – {hi}")
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if lines:
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lines.append("")
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lines.append("Flights:")
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lines.append("")
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all_flights = (best_flights + other_flights)[:max_results]
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for i, flight in enumerate(all_flights, 1):
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segments = flight.get("flights", []) or []
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total_duration = flight.get("total_duration", 0) # minutes
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price = flight.get("price", 0)
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layovers = flight.get("layovers", []) or []
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hours, minutes = divmod(total_duration, 60)
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duration_str = f"{hours}h {minutes}m" if hours > 0 else f"{minutes}m"
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cheapest_tag = " (CHEAPEST)" if i == 1 and best_flights else ""
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lines.append(f"#{i}: {price}{cheapest_tag}")
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lines.append("")
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for seg in segments:
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dep = seg.get("departure_airport", {}) or {}
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arr = seg.get("arrival_airport", {}) or {}
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airline = seg.get("airline", "?")
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flight_num = seg.get("flight_number", "?")
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seg_dur = seg.get("duration", 0)
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seg_h, seg_m = divmod(seg_dur, 60)
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seg_dur_str = f"{seg_h}h {seg_m}m" if seg_h > 0 else f"{seg_m}m"
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lines.append(f" {airline} {flight_num}")
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lines.append(f" {dep.get('id', '?')} {dep.get('time', '?')} -> {arr.get('id', '?')} {arr.get('time', '?')}")
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lines.append(f" Duration: {seg_dur_str}")
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lines.append("")
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if layovers:
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parts = []
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for lo in layovers:
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lo_dur = lo.get("duration", 0)
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lo_h, lo_m = divmod(lo_dur, 60)
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parts.append(f"{lo.get('id', '?')} ({lo_h}h {lo_m}m)")
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lines.append(f" Layovers: {' -> '.join(parts)}")
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lines.append("")
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lines.append(f" Total duration: {duration_str}")
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emissions = flight.get("carbon_emissions") or {}
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if emissions.get("this_flight") is not None:
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lines.append(f" CO2: {emissions['this_flight']}g")
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lines.append("")
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return "\n".join(lines).rstrip()
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# ── Tool implementation ────────────────────────────────────────────────────────
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_DATE_RE = re.compile(r"^\d{4}-\d{2}-\d{2}$")
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_IATA_RE = re.compile(r"^[A-Za-z]{3}$")
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_VALID_CABINS = {"economy", "premium_economy", "business", "first"}
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def _validate_int(value: Any, name: str, lo: int, hi: int, default: int) -> int:
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if value is None:
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return default
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try:
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v = int(value)
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except (TypeError, ValueError):
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raise _ValidationError(f"'{name}' must be an integer between {lo} and {hi}.")
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if v < lo or v > hi:
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raise _ValidationError(f"'{name}' must be between {lo} and {hi} (got {v}).")
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return v
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class _ValidationError(Exception):
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"""Raised for invalid tool arguments; message is returned to the LLM."""
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def _serpapi_search_flights(args: dict) -> str:
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# ── Required params ────────────────────────────────────────────────────────
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departure_id = (args.get("departure_id") or "").strip().upper()
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arrival_id = (args.get("arrival_id") or "").strip().upper()
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outbound_date = (args.get("outbound_date") or "").strip()
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if not departure_id:
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raise _ValidationError("Missing required parameter 'departure_id' (3-letter IATA airport or city code, e.g. 'JFK', 'MIL').")
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if not _IATA_RE.match(departure_id):
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raise _ValidationError(f"'departure_id' must be exactly 3 ASCII letters (got '{departure_id}'). Use an airport code (e.g. 'JFK') or a city code (e.g. 'NYC', 'MIL', 'LON').")
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if not arrival_id:
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raise _ValidationError("Missing required parameter 'arrival_id' (3-letter IATA airport or city code).")
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if not _IATA_RE.match(arrival_id):
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raise _ValidationError(f"'arrival_id' must be exactly 3 ASCII letters (got '{arrival_id}'). Use an airport code (e.g. 'FCO') or a city code (e.g. 'ROM').")
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if not outbound_date:
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raise _ValidationError("Missing required parameter 'outbound_date' (YYYY-MM-DD).")
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if not _DATE_RE.match(outbound_date):
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raise _ValidationError(f"'outbound_date' must be in YYYY-MM-DD format (got '{outbound_date}').")
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# ── Optional params ────────────────────────────────────────────────────────
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return_date = (args.get("return_date") or "").strip() or None
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if return_date and not _DATE_RE.match(return_date):
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raise _ValidationError(f"'return_date' must be in YYYY-MM-DD format (got '{return_date}').")
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adults = _validate_int(args.get("adults"), "adults", 1, 10, 1)
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children = _validate_int(args.get("children"), "children", 0, 8, 0)
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infants_in_seat = _validate_int(args.get("infants_in_seat"), "infants_in_seat", 0, 4, 0)
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infants_on_lap = _validate_int(args.get("infants_on_lap"), "infants_on_lap", 0, 4, 0)
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stops_raw = args.get("stops")
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stops: int | None = None
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if stops_raw is not None:
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try:
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stops = int(stops_raw)
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except (TypeError, ValueError):
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raise _ValidationError("'stops' must be 0 (non-stop only), 1 (max 1 stop), or 2 (max 2 stops).")
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if stops not in (0, 1, 2):
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raise _ValidationError(f"'stops' must be 0, 1, or 2 (got {stops}).")
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currency = (args.get("currency") or "EUR").strip().upper()
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if not re.match(r"^[A-Z]{3}$", currency):
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raise _ValidationError(f"'currency' must be a 3-letter ISO code (got '{currency}').")
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preferred_cabins = args.get("preferred_cabins")
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if preferred_cabins is not None:
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preferred_cabins = str(preferred_cabins).strip().lower()
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if preferred_cabins not in _VALID_CABINS:
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raise _ValidationError(f"'preferred_cabins' must be one of: {', '.join(sorted(_VALID_CABINS))}.")
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hl = args.get("hl") or "en"
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max_results = _validate_int(args.get("max_results"), "max_results", 1, 50, 10)
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# ── Build SerpAPI params ───────────────────────────────────────────────────
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api_params: dict[str, Any] = {
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"engine": "google_flights",
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"departure_id": departure_id,
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"arrival_id": arrival_id,
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"outbound_date": outbound_date,
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"adults": adults,
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"children": children,
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"infants_in_seat": infants_in_seat,
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"infants_on_lap": infants_on_lap,
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"currency": currency,
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"hl": hl,
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}
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if return_date:
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api_params["return_date"] = return_date
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api_params["type"] = "1" # round-trip
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else:
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api_params["type"] = "2" # one-way
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if stops is not None:
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api_params["stops"] = stops
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if preferred_cabins:
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api_params["preferred_cabins"] = preferred_cabins
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# ── Call ───────────────────────────────────────────────────────────────────
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try:
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data = _serpapi_request(api_params)
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except Exception as e:
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return _format_api_error(e)
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if data.get("error"):
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return f"Error: SerpAPI returned an error: {data['error']}"
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return _format_flight_results(data, max_results)
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# ── Tool manifest ──────────────────────────────────────────────────────────────
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TOOLS = [
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{
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"name": "serpapi_search_flights",
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"description": (
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"Search one-way or round-trip flights on Google Flights via SerpAPI. "
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"Returns a plain-text list of routes with price, airline + flight number, "
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"departure/arrival times, segment durations, total duration, layovers, "
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"and CO2 emissions. The first result is typically the cheapest.\n"
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"Both airport codes (3 letters, e.g. 'JFK', 'FCO') and city codes "
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"(3 letters covering all airports of a city, e.g. 'NYC', 'ROM', 'MIL', "
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"'LON') are accepted for departure_id and arrival_id — prefer city codes "
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"when the user does not name a specific airport."
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),
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"inputSchema": {
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"type": "object",
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"properties": {
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"departure_id": {
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"type": "string",
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"description": "Departure airport or city code — exactly 3 ASCII letters. Examples: 'JFK' (New York JFK), 'MIL' (any Milan airport), 'LON' (any London airport), 'ROM' (any Rome airport).",
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},
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"arrival_id": {
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"type": "string",
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"description": "Arrival airport or city code — exactly 3 ASCII letters. See departure_id for examples.",
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},
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"outbound_date": {
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"type": "string",
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"description": "Outbound date in YYYY-MM-DD format (e.g. '2026-08-01').",
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},
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"return_date": {
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"type": "string",
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"description": "Return date in YYYY-MM-DD for round-trip searches. Omit for one-way.",
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},
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"adults": {
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"type": "integer",
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"description": "Number of adult passengers (12+). Default 1, max 10.",
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},
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"children": {
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"type": "integer",
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"description": "Number of children (2-11). Default 0, max 8.",
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},
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"infants_in_seat": {
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"type": "integer",
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"description": "Number of infants occupying a seat. Default 0, max 4.",
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},
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"infants_on_lap": {
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"type": "integer",
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"description": "Number of infants on an adult's lap (under 2). Default 0, max 4.",
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},
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"stops": {
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"type": "integer",
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"enum": [0, 1, 2],
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"description": "Maximum number of stops: 0 = non-stop only, 1 = max 1 stop, 2 = max 2 stops. Omit to allow any.",
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},
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"currency": {
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"type": "string",
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"description": "ISO 4217 currency code for prices (e.g. 'EUR', 'USD', 'GBP'). Default 'EUR'.",
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},
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"preferred_cabins": {
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"type": "string",
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"enum": ["economy", "premium_economy", "business", "first"],
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"description": "Cabin class filter. Omit to search all cabins.",
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},
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"hl": {
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"type": "string",
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"description": "Language code for results (e.g. 'en', 'it', 'fr'). Default 'en'.",
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},
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"max_results": {
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"type": "integer",
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"description": "Maximum number of flight options to return. Default 10, max 50.",
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},
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},
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"required": ["departure_id", "arrival_id", "outbound_date"],
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},
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},
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]
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# ── JSON-RPC dispatch ──────────────────────────────────────────────────────────
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TOOL_DISPATCH = {
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"serpapi_search_flights": _serpapi_search_flights,
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}
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def _ok(req_id: Any, result: Any) -> str:
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return json.dumps({"jsonrpc": "2.0", "id": req_id, "result": result})
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def _text_result(req_id: Any, text: str, is_error: bool = False) -> str:
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payload: dict = {
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"jsonrpc": "2.0",
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"id": req_id,
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"result": {"content": [{"type": "text", "text": text}]},
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}
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if is_error:
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payload["result"]["isError"] = True
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return json.dumps(payload)
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||||
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def handle_request(msg: dict) -> str | None:
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method = msg.get("method", "")
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req_id = msg.get("id")
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if method == "initialize":
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return _ok(req_id, {
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"protocolVersion": "2024-11-05",
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"capabilities": {"tools": {}},
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"serverInfo": {
|
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"name": "serpapi_flights",
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"version": "2.0.0",
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||||
},
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||||
})
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||||
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||||
if method == "notifications/initialized":
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return None
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||||
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||||
if method == "tools/list":
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return _ok(req_id, {"tools": TOOLS})
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||||
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if method == "tools/call":
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||||
params = msg.get("params", {})
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tool_name = params.get("name", "")
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||||
tool_args = params.get("arguments", {}) or {}
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||||
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handler = TOOL_DISPATCH.get(tool_name)
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if handler is None:
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||||
return _text_result(req_id, f"Error: Unknown tool: {tool_name}", is_error=True)
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||||
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||||
try:
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text = handler(tool_args)
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||||
except _ValidationError as e:
|
||||
return _text_result(req_id, f"Error: {e}", is_error=True)
|
||||
except Exception as e:
|
||||
log(f"Unhandled exception in tool '{tool_name}': {e}")
|
||||
return _text_result(req_id, f"Error: Internal error in tool '{tool_name}': {e}", is_error=True)
|
||||
|
||||
is_err = text.startswith("Error:")
|
||||
return _text_result(req_id, text, is_error=is_err)
|
||||
|
||||
return json.dumps({
|
||||
"jsonrpc": "2.0",
|
||||
"id": req_id,
|
||||
"error": {"code": -32601, "message": f"Method not found: {method}"},
|
||||
})
|
||||
|
||||
|
||||
# ── Main loop ──────────────────────────────────────────────────────────────────
|
||||
|
||||
def main() -> None:
|
||||
log("Starting SerpAPI Google Flights MCP server")
|
||||
# Validate API key eagerly so configuration errors surface at startup.
|
||||
_get_api_key()
|
||||
try:
|
||||
for line in sys.stdin:
|
||||
line = line.strip()
|
||||
if not line:
|
||||
continue
|
||||
try:
|
||||
msg = json.loads(line)
|
||||
except json.JSONDecodeError as e:
|
||||
log(f"Invalid JSON input: {e}")
|
||||
continue
|
||||
|
||||
resp = handle_request(msg)
|
||||
if resp is not None:
|
||||
sys.stdout.write(resp + "\n")
|
||||
sys.stdout.flush()
|
||||
except KeyboardInterrupt:
|
||||
pass
|
||||
|
||||
|
||||
if __name__ == "__main__":
|
||||
main()
|
||||
Reference in New Issue
Block a user