Asking for an answer

Ask one question and get a written answer with the sources it rests on, from any answer provider, in a single call.

answer() asks one question and returns the backend’s own written answer with the sources it rests on, in one call. It sits between search(), which returns the pages, and research(), a job of minutes.

Three steps to a first answer:

1. Install with the answer extra: pip install "webrouter[answer]" (make setup in a clone installs every extra).
2. Set one answer backend’s key in your environment or .env, for example PERPLEXITY_API_KEY — Configuration lists each one’s variable.
3. Ask:

from web_router import WebRouter

with WebRouter() as router:
    response = router.answer("who won the 2022 world cup final")  # the one backend you hold a key for

print(response.answer)
for citation in response.citations:
    print(citation.field or "-", citation.url)

Argentina won, beating France 4-2 on penalties after a 3-3 draw through extra time.[2]
- https://football.fandom.com/wiki/2022_FIFA_World_Cup_Final
[2] https://www.world-cup-schedule.com/blog/who-won-2022-world-cup-argentina-france-final
...

With more than one key set, name the backend: router.answer(q, provider="linkup"). Which one: they score alike on accuracy (see the answer comparison), so pick on what you need — Linkup had the lowest median latency in that scan (0.9 s); Perplexity, You.com and Linkup take source filters (domains, recency); Perplexity, You.com, Exa and Linkup tie each source to a sentence. examples/answer.py runs the whole flow, errors included.

Nothing here writes, joins or edits the answer: it is the backend’s, as it came. An empty one comes back as "" rather than an error, with its sources and raw, so “the backend had nothing” reads differently from a failure. Where a backend marks which source backs which sentence, the marker is in citation.field; where it does not (Parallel), every citation backs the answer as a whole. outcome is partial only when the backend says it stopped early.

The options are include_domains, exclude_domains, country, locale and recency ("day", "week", "month" or "year"). Windows count whole days; where the router sets the start date itself (Linkup), it counts back from today’s date in UTC. A backend that does not map one raises UnsupportedParameterError before anything is sent — the answer table says which backend maps what.

With provider unset, the router’s default answers when it is an answer backend. On the usual default, auto, that is every answer backend you hold a key for (in the environment or in provider_config), in the order make chains ranks them on 300 benchmark questions — accuracy first, and where accuracy is too close to tell apart, the cheaper at list price: Perplexity, You.com, Linkup, Parallel, Exa, then Brave, which the scan has not measured. A backend that does not map an option you set is passed over without being called; one that fails, or answers with nothing, is passed over for the next, and each one tried bills. provider_config={"auto": {"chain": {"answer": [...]}}} sets the order. With no key, the call raises NoAnswerProviderError (a ProviderNotFoundError) naming the variables to set. On a router whose default is not an answer backend (WebRouter("nimble")), the one answer backend you hold a key for serves the call; with several, name one, or pass provider="auto".

“Answer” means two other things nearby. SearchResponse.answer is an answer a search backend volunteered beside its results, unasked (You.com’s knowledge panel); answer() is one you asked for, with its sources.