## Where Parts 1 and 2 left off [Part 1](/article/building-a-budget-travel-pipeline) built a flexible flight search pipeline by forking [`fli`](https://github.com/RobertoReale/fli) to add `--min-duration` and `--max-duration`, then wiring it to an AI agent via MCP. [Part 2](/article/budget-travel-pipeline-applied) ran the whole thing — flights, accommodation, price verification — and documented the gap that makes the pipeline unreliable if you skip it: the free [`trvl`](https://github.com/MikkoParkkola/trvl) prices are Google Hotels teasers, not bookable rates. A hotel listed at €46/night was €269 on Booking.com for the same dates and party. The gap is not occasional; it is structural. Eight days after Part 2 published, the maintainer opened an issue. --- ## The arc [Mikko Parkkola](https://github.com/MikkoParkkola), who built `trvl`, found the article and opened issue #1 on this blog's repo asking for a retest against a newer version. The framing was direct: the verification paths had changed since what I'd tested; were the same gaps still there? The retest protocol: same destination (Ischia, 2026-07-30 → 2026-08-04, 2 adults, 5 nights, EUR), every command tested systematically, compared against [`serpapi_verified.py`](https://github.com/RobertoReale/travel-search)'s reference output, results reported exactly — including when something broke. This is the only thing that makes a retest useful to a maintainer: reproducible facts, not impressions. **Turn 1.** Retest report sent June 12. The gap had narrowed substantially — from ~5.8× (original article) to ~1.4× — but remained consequential for a decision-making pipeline. Two blockers: `prices: null` in the `trvl serpapi` output for all hotels, and `trvl rooms` failing on every Ischia property (no Google place IDs for island hotels in the index). **Turn 2 (< 24h).** Mikko shipped v1.9.1. The fix: when SerpAPI is configured, `trvl prices` now does a list → detail call sequence, recovering per-provider data where v1.8.0 returned `providers: null`. For Hotel Continental Mare, that meant 10 verified provider rows instead of nothing. He also fixed the fallback safety: a broad city string could no longer silently match to an unrelated lead-in price. **Turn 3.** Retesting v1.9.1, one command broke in a new way. The name-based fallback — querying `trvl prices` by hotel name instead of a Google place ID, with SerpAPI active — resolved to a completely wrong hotel: ```bash trvl prices "Hotel Villa Maria" --location "Sant Angelo Ischia Italy" \ --checkin 2026-07-30 --checkout 2026-08-04 --currency EUR --format json ``` v1.9.1 returned `"name": "Miramare Sea Resort & Spa"` — a different 5-star resort — with 9 "verified" providers at €2,336–€2,830. In v1.8.0, this had returned `providers: null`. The new SerpAPI path made the failure louder: instead of safe silence, confident wrong prices for the wrong property. An AI agent consuming `providers[0].price` without also checking `name` would act on a figure 2–3× too high, for a hotel it hadn't asked for. **Turn 4 (same day).** Mikko confirmed the mechanism and shipped v1.9.2. The fix: the name-based fallback now compares the requested property name against the returned property name; if they don't match, it returns `providers: null` rather than presenting a different hotel as booking-ready. A regression test pinned on the exact case. The v1.9.2 retest result was better than `providers: null`: ```bash trvl prices "Hotel Villa Maria" --location "Sant Angelo Ischia Italy" \ --checkin 2026-07-30 --checkout 2026-08-04 --currency EUR --format json ``` v1.9.2 returned `"name": "Hotel Villa Maria Sant'Angelo d'Ischia"` — the correct property — with 13 verified providers ranging €620–€1,274. The fix doesn't just reject mismatches: the name matching now resolves correctly when the hotel exists. Miramare Sea Resort & Spa no longer passes; the real Hotel Villa Maria does. Closing comment from Mikko: *"This is the kind of report that makes the tool genuinely safer for an agent pipeline."* --- ## What changed: v1.8.0 → v1.9.1 → v1.9.2 | Fix | v1.8.0 | v1.9.1 | v1.9.2 | |-----|--------|--------|--------| | `trvl prices` with valid Google place ID + SerpAPI | `providers: null` | ✅ per-provider matrix | ✅ per-provider matrix | | Trust labeling (`price_basis` / `price_confidence`) | absent | ✅ `lead_in / unverified` on free results | ✅ same | | Provider breakdown in `trvl serpapi` | null for all | ✅ ~50% (those with `property_token`) | ✅ same | | Fallback safety (generic city string) | silent wrong match | ✅ `providers: null` + notice | ✅ same | | `€` encoding in string fields | broken (`Ôé¼`) | ✅ fixed | ✅ same | | Name-based fallback with SerpAPI active | `providers: null` (safe) | ❌ wrong hotel, "verified" | ✅ correct hotel or `providers: null` | The v1.9.2 change is in the last row. It's the one that matters most for an agent pipeline where the model may call `trvl prices "Hotel Name"` rather than `trvl prices `. --- ## Three issues After the fix landed, Mikko opened three issues crediting the findings: | Issue | What | Why it matters for this pipeline | |-------|------|----------------------------------| | **[#167](https://github.com/MikkoParkkola/trvl/issues/167)** | Docs: surface `find_trip_window`, multi-pax, verified-accommodation path | `find_trip_window` already exists in trvl — the tool Roberto forked `fli` to add, not knowing trvl had it. Better docs would have made the fork unnecessary from day one. | | **[#168](https://github.com/MikkoParkkola/trvl/issues/168)** | Hotels: link-durability — drop dead `aclk`/`clk` redirects, emit durable Booking.com fallback | The link-expiry problem from Part 2. When it lands, reliable booking links from trvl directly. | | **[#170](https://github.com/MikkoParkkola/trvl/issues/170)** | CLI: expose `--min-duration`/`--max-duration` on `trvl dates` | Literally the same feature from the fli fork, coming natively to trvl. | All three shipped as merged PRs on main, along with two additional ones. The next section covers what each did. --- ## What landed: v1.10 batch on main All six PRs merged and released as [v1.10.0](https://github.com/MikkoParkkola/trvl/releases/tag/v1.10.0) on 2026-06-14. | PR | Issue | What it does | |----|-------|-------------| | **[#172](https://github.com/MikkoParkkola/trvl/pull/172)** | [#167](https://github.com/MikkoParkkola/trvl/issues/167) | `find_trip_window`, multi-pax, and the full one-binary pipeline path documented in `AGENTS.md`. `ROADMAP.md` added. | | **[#173](https://github.com/MikkoParkkola/trvl/pull/173)** | [#168](https://github.com/MikkoParkkola/trvl/issues/168) | Link triage native: strips `travel/clk` vacation-rental redirects, tags links `stable` vs `expiring`, always emits a durable Booking.com deep-link as `booking_fallback_url`. | | **[#174](https://github.com/MikkoParkkola/trvl/pull/174)** | [#170](https://github.com/MikkoParkkola/trvl/issues/170) | `--min-duration` and `--max-duration` on `trvl dates`. The exact CLI gap that motivated the fli fork, now native. | | **[#175](https://github.com/MikkoParkkola/trvl/pull/175)** | [#169](https://github.com/MikkoParkkola/trvl/issues/169), [#171](https://github.com/MikkoParkkola/trvl/issues/171) | `tourist_tax_note` and `tax_added_at_checkout` as native fields in `hotel_prices` MCP output — the "Two kinds of tax" rules from the guide, made part of the data model. | | **[#176](https://github.com/MikkoParkkola/trvl/pull/176)** | — | trvl README adds an "Independent coverage" section linking this three-part series, crediting it for shaping the v1.10 trust roadmap. | | **[#177](https://github.com/MikkoParkkola/trvl/pull/177)** | — | Registry listings (Smithery, MCPHub, Cursor Directory) added; social-proof section repositioned above "What it looks like". | Each of the feature PRs carries an explicit credit line. PR #173 notes it is *"trvl's native version of his travel-search triage"*; PR #175 notes *"these are his trust rules made native."* PR #176 makes the citation permanent in the tool's official README. Run `go install github.com/MikkoParkkola/trvl/cmd/trvl@latest` to install v1.10.0. --- ## One correction from Part 2 Part 2 described `hotel-rates-mcp` as a packaged MCP server you could install with `pip` and wire into `.mcp.json`. That package has not been published. The actual implementation is [`serpapi_verified.py`](https://github.com/RobertoReale/travel-search) in the `travel-search` repo — a standalone script, not an MCP tool. The aspiration was real; the package wasn't built before the article went out. The guide below doesn't reference it. `serpapi_verified.py` is a post-processing step you run after the agent, not a tool the agent calls. --- ## The complete setup guide: as of 2026-06-14, trvl v1.10.0 The overall structure from Part 2 is still correct. What changed: the `.mcp.json` (one fewer server), the verification step in the prompt (no `hotel-rates` tool), and the note on name-based lookups. ### What you need - Python 3.9+, Node 18+ (for MCP server wiring) - `fli` from the fork (only required if you use `--return-time` — see below) - `trvl` v1.10.0+ - A free SerpAPI key: [serpapi.com](https://serpapi.com/) — 250 searches/month, no credit card ### Install **fli, from the fork:** ```bash pip install git+https://github.com/RobertoReale/fli.git@feature/window-duration fli dates --help # verify --min-duration and --max-duration appear ``` *Windows only:* `set PYTHONIOENCODING=utf-8` before any `fli` command to avoid encoding errors on destination names. *As of trvl v1.10.0, `trvl dates` supports `--min-duration`/`--max-duration` natively — the fli fork is only needed if you also use `--return-time` (time-of-day filtering, [PR #196](https://github.com/punitarani/fli/pull/196) still open upstream). If you don't use `--return-time`, skip the fork entirely.* **trvl v1.10.0:** ```bash # macOS brew install MikkoParkkola/trvl/trvl brew upgrade trvl trvl version # should print 1.10.0 ``` Windows: download `trvl_1.10.0_windows_amd64.tar.gz` from the [v1.10.0 release](https://github.com/MikkoParkkola/trvl/releases/tag/v1.10.0), extract, put `trvl.exe` on your PATH. **SerpAPI key:** ```bash export SERPAPI_KEY="your_key_here" # PowerShell: $env:SERPAPI_KEY="your_key_here" ``` ### Folder structure ``` ~/summer-vacation/ ├── .mcp.json └── results/ ``` ### `.mcp.json` Two servers: `fli` and `trvl`. Drop the `hotel-rates` server from Part 2 — it referenced a package that hasn't been published: ```json { "mcpServers": { "fli": { "command": "fli-mcp" }, "trvl": { "command": "trvl", "args": ["mcp"] } } } ``` Set `SERPAPI_KEY` in your environment *before* launching the agent. Then: ```bash cd ~/summer-vacation claude ``` Run `/mcp` — both `fli` and `trvl` should show `connected`. ### Which command does what | What you want | Command | Notes | |---------------|---------|-------| | Flights — flexible date window | `trvl dates BGY NAP --from 2026-07-22 --to 2026-08-01 --round-trip --min-duration 4 --max-duration 7 --currency EUR` | Native in v1.10.0. Use fli fork only if you also need `--return-time`. The agent calls `find_trip_window` via MCP. | | Hotels — verified prices for ranking | `trvl serpapi "Ischia" --checkin 2026-07-30 --checkout 2026-08-04 --currency EUR --format json` | Use this, not `trvl hotels`. Routes through SerpAPI; prices are real. | | Hotels — per-provider matrix + OTA links | `trvl prices --checkin 2026-07-30 --checkout 2026-08-04 --currency EUR --format json` | Needs place ID from `trvl hotels --format json`. Includes `booking_fallback_url` and `link_durability` in v1.10.0. | | Deeplinks, tax-aware, link-validated | `python serpapi_verified.py "Ischia" 2026-07-30 2026-08-04 --adults 2 --top 8` | Post-processing, not an agent tool. From [travel-search](https://github.com/RobertoReale/travel-search). | **Do not use `trvl hotels` for any price you rank on.** It returns Google Hotels teasers — the list-preview minimum, not what you'll pay. Use `trvl serpapi` instead: it costs one SerpAPI search per query and returns verified prices. ### Verification tiers Three levels, each costs more quota: **Tier 1 — `trvl serpapi`** returns verified list-level prices via SerpAPI. `price_confidence: verified` per hotel. About half the hotels also have a `property_token`, enabling a detail call with per-provider breakdown. The other half get a verified total but no OTA breakdown. Good for ranking across many hotels quickly. **Tier 2 — `trvl prices `** returns the per-provider matrix with individual OTA links, if you have the Google place ID. Get it from `trvl hotels --format json`. This is the best native path for the final booking step: verified total *and* links to the actual OTA listings. **Tier 3 — `serpapi_verified.py`** calls SerpAPI list + detail per hotel, recovers per-provider totals and booking deeplinks, ranks on the tax-inclusive total, flags providers that add tax at checkout, HTTP-validates links. Works for hotels without a place ID. Run it after the agent to get the most reliable booking links before committing. For island destinations in peak season (Ischia and similar): `trvl rooms` still fails — most hotels don't appear in the Google place-ID index. Use tier 3 for those. ### Name-based lookup: safe in v1.9.2+, but still not the automation path The v1.9.2 fix means `trvl prices "Hotel Name" --location "..."` now either resolves correctly or returns `providers: null`. It's no longer dangerous. But for an automated pipeline, `trvl prices ` remains the right call when you have the ID — a name lookup adds a fuzzy-match step that a place ID skips. Use the name path for one-off lookups or when no place ID is available; use the ID path for anything unattended. --- ## The prompt The four-step template from Part 2 is still valid. Three changes from that version: the `.mcp.json` has one fewer server, the flight search in Step 1 uses `trvl dates` / `find_trip_window` (native in v1.10.0) instead of the fli MCP, and the verification in Step 2 uses `trvl serpapi` instead of the `hotel-rates` tool. A no-code prompt builder is in [`prompt-builder.html`](https://github.com/RobertoReale/travel-search/blob/master/prompt-builder.html) in the `travel-search` repo — open it in a browser, fill in the form, copy the generated prompt. ``` Budget travel pipeline TRIP VARIABLES - Departure airports: [e.g. BGY, MXP, LIN] (IATA airport codes; search each as a separate roundtrip) - Overall availability: [e.g. Jul 22 – Aug 6] (earliest you can leave – latest you must be back) - Stay duration: [e.g. 5] nights - Travellers / Guests: [e.g. 2] adults - Outbound flight from home: [e.g. before 16:00] - Return flight from destination: [e.g. after 16:00] ADVANCED FILTERS (Optional - Remove or modify as needed) [Flights] - Flight Stops: [e.g. NON_STOP, ONE_STOP, or ANY] - Flight Class: [e.g. ECONOMY, BUSINESS] - Airlines (Include/Exclude): [e.g. Exclude FR, Include U2] - Airline Alliances: [e.g. SKYTEAM, STAR_ALLIANCE, ONEWORLD] - Layover limits: [e.g. max 120 minutes] [Accommodation - General] - Property Type: [hotel, apartment, hostel, resort, bnb, villa, or ANY] - Room Type: [entire_home, private_room, shared_room, hotel_room, or ANY] - Quality minimums: [e.g. 3 stars, 8.0/10 user rating] - Max budget: [e.g. max €150/night] - Max distance from center: [e.g. 5 km] [Accommodation - Perks & Rules] - Meal Plan: [e.g. breakfast included, or ANY] - Cancellation: [e.g. free cancellation only] - Eco-certified: [e.g. TRUE or FALSE] [Accommodation - Rentals specific (Airbnb/Apartments)] - Minimum layout: [e.g. 2 bedrooms, 1 bathroom] - Superhost only: [e.g. TRUE or FALSE] [Accommodation - Verification & Safety] - Trusted Providers (OTA Whitelist): [e.g. "Booking.com, Expedia.com" or "ALL"] - Verify Links: [e.g. TRUE (drop dead links)] DESTINATIONS (sea/beach access only) - [IATA] ([City]) — [transit note, e.g. "ferry to Ischia ~1 hr"] - [IATA] ([City]) — [access note] ... Step 1 — Flights (trvl MCP server) Using the TRIP VARIABLES and ADVANCED FILTERS above: - Search each Departure airport as a separate roundtrip using the find_trip_window tool. - Set min-duration and max-duration from the Stay duration range (same value = fixed length). - Calculate the outbound search window: start date = start of Overall availability. end date = end of Overall availability MINUS Stay duration. (e.g. If availability ends Aug 6 and stay is 5 nights, your end date is Aug 1). - Map Travellers to the adults argument. - Apply all specified [Flights] filters (Stops, Class, Airlines, Alliances, Layover) to the tool. - Multiply the single adult fare by Travellers for the trip total. Sort by cheapest roundtrip. Save all results to results/flights.md. Step 2 — Accommodation (trvl MCP server, run searches in parallel) For the top [e.g. 5] flight options, search accommodation at the actual destination: - Guests: use Travellers variable. - Dates: check-in = outbound flight date, check-out = return flight date. - Use trvl serpapi (not trvl hotels). SERPAPI_KEY must be set in the environment. The free trvl hotels prices are Google Hotels teasers — do not rank on them. trvl serpapi returns SerpAPI-verified prices (price_confidence: verified). - Filters: apply all [Accommodation] preferences natively where the tool supports them. - Rank on the SerpAPI-verified total, never the per-night teaser. - If a Google place ID is available for a shortlisted hotel (from trvl hotels --format json output), use trvl prices to get the per-provider breakdown with OTA links. - Note which hotels return providers: null — those need serpapi_verified.py as a post-processing step for reliable booking deeplinks. - Budget: apply max budget to verified total ÷ nights. Save raw results per date window to results/hotels_[dates].json. Step 3 — Evaluate a) Anomalies: flag any result that bypassed the filters (e.g. a B&B appearing under a hotel/3-star filter, or a 0-star property passing a star minimum). Keep in the JSON for reference; exclude from the final ranking. b) Price & tax: rank on the verified TOTAL (taxes included), never the per-night teaser. Prefer the all-in provider (Booking.com quotes taxes in; some others add them at checkout — flag those). Any local tourist tax (e.g. city tax) is paid in cash at the property, is in no online total, and is the same for every provider — note it as a separate cash cost, but do not estimate a figure or fold it into the ranking. Discard any hotel whose only links are vacation-rental redirects (google.com/travel/clk) that 404 — keep working OTA links. c) Verify: web-search each candidate. Confirm it is currently operating. Collect review highlights — cleanliness, noise levels, distance from sea, recurring complaints. d) Location: for each hotel, note which part of the destination it is in, distance to the nearest beach, and distance to the ferry port or airport. Assess whether the position suits a sea-access trip. Step 4 — Final output Rank all combinations by total trip cost (flight + verified accommodation total). Exclude any option with a critical red flag. Present the top [N_FINAL] valid options only — do not include filtered-out results in the final report. For each valid option include: - Total cost (flight + verified hotel total, itemised; note any property-collected tourist tax separately as a cash cost, without inventing a figure) - Hotel: rating, review count, star category, key amenities - Location: neighbourhood · minutes to nearest beach · minutes to ferry/transit - Agent verdict (one sentence) - Google Flights link for the flight - Working per-provider hotel booking link (an OTA link that lands on the rate — not a generic search page, not a vacation-rental redirect) Export to results/final-results.md. ``` --- ## What still doesn't work **`trvl rooms` on Italian islands.** Most Ischia hotels don't appear in the Google place-ID index. No place ID means no per-provider matrix from `trvl prices`. Use `trvl serpapi` for pricing and `serpapi_verified.py` for booking links. **~50% property_token coverage.** SerpAPI returns `property_token` for roughly half the properties in a list result. For the other half, `trvl serpapi` returns a verified total but no per-provider breakdown — just the minimum across providers. `serpapi_verified.py` makes its own detail call and covers more hotels, but coverage still isn't 100%. **The teaser remains in `trvl hotels`.** `trvl hotels` still returns the teaser price — that's what the command is for: discovery (which hotels exist in the area), not pricing. The distinction is: `trvl hotels` for the list, `trvl serpapi` for the verified price, `trvl prices ` for the per-provider booking step. --- ## The arc, closed The sequence: a blog article documented a real problem → a maintainer opened an issue asking for a retest → two fixes shipped in 48 hours → three new issues opened citing the findings → five PRs merged → v1.10.0 released. Every workaround built for this series now exists natively in the tool: the link triage from `serpapi_verified.py`, the tax distinction from the guide, the flexible date search from the `fli` fork. Each feature PR carries an explicit credit line. The README links the series. The loop closed the same day it opened. This was a first open source contribution arc — not a code PR, but a structured field report. The contribution was the article. The artifact is a safer tool for everyone building on it. --- ## Caveats All of these tools reverse-engineer internal endpoints that can change without notice. Using them sits in a legal grey area — most platforms prohibit automated access in their terms of service. Use them for personal research. LLMs are non-deterministic. The same prompt run twice may produce different tool call sequences, query a different subset of destinations, or occasionally skip a route. Prices reflect the moment the search ran — a verified `trvl serpapi` total is accurate at that instant, not locked. As of trvl v1.10.0, the fli fork is only needed for `--return-time` (departure/arrival time filtering, [PR #196](https://github.com/punitarani/fli/pull/196) still open upstream). If that PR merges, install from the upstream `fli` repo instead. For everything else — flexible stay windows, verified hotel prices, per-provider booking links — trvl covers the full pipeline alone. --- *Author: Roberto Reale* *Source: https://blog-roberto-reale.vercel.app/article/budget-travel-pipeline-fixed*