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GET /v1/podcasts/episodes/search finds dialogue inside podcast episodes. Each result is a segment of an episode, returned with bounded transcript windows centered on the highest-relevance dialogue lines (flagged is_match: true) and any highlight clips that overlap the segment.
Available to MCP agents as particle_podcast_search_transcripts.
This endpoint searches dialogue, not podcasts. To find a podcast by name, use GET /v1/podcasts/search?q=…. To resolve a podcast from an Apple / Spotify / YouTube identifier, use GET /v1/podcasts/lookup.

When to use Episode search vs Mentions

The Particle podcast surface ships two complementary dialogue-search endpoints. Pick by what you’re really asking. Episode search ranks segments by relevance. Mentions returns episodes with all of their mention windows in time order. Different shapes, different jobs.

semantic_search — search by meaning

Vector search is the right tool when the surface words in dialogue might not match the surface words in your query. Two speakers can discuss the same idea using totally different vocabulary, and a lexical engine misses both. Express your query the way you’d describe the topic to a colleague — full sentences are welcome.
The above will surface segments that talk about restrictive monetary policy, the FOMC’s bias, PCE moderation, or real rates being too high — even when the words “hawkish” or “Fed” never appear. What semantic_search is not good at:

keyword_search — search by exact tokens (BM25)

Use this when the exact form of a token matters: company tickers, drug names, model numbers, hashtags. Tokens are matched after the same normalization the index applies (lowercased, English tokenizer, no stemming); punctuation splits tokens, and single-letter tokens without a digit are dropped, so spell terms out rather than abbreviating to one character. Multi-word queries are matched as a bag of tokens, ranked by BM25. Every token you type must appear somewhere in the matched passage. That is what makes results trustworthy — a hit is guaranteed to contain your terms — but it also means a loose pile of related words that never co-occur in one passage returns nothing. Pass keyword_match=ranked for that case and the words steer relevance instead of excluding anything. To require an exact ordered phrase rather than independent tokens, wrap it in double quotes — keyword_search="machine learning". Multiple quoted phrases must all appear ("central bank" "interest rates"). Quoted phrases filter under both modes, so to relax a phrase remove its quotes rather than switching mode. A quoted phrase requires those words adjacent and in order in the segment’s spoken dialogue. A speaker’s own name is not indexed as dialogue — searching "Graham Duncan" returns segments where the name appears in what was said, not every segment he speaks in. Use entity_id or /v1/podcasts/mentions to find a person’s appearances instead. Adjacency is measured across the segment’s dialogue as a whole, so in rare cases a phrase can straddle the break between two consecutive lines. There is no boolean OR — a bare OR is matched as an ordinary word. Send alternatives as separate requests.
When you want to rank by an idea and a specific term at once, send both. Each leg runs independently — vector similarity and BM25 — and the two result sets are fused via reciprocal rank fusion. Under the default keyword_match=required the fusion is an intersection: your keyword tokens filter both legs, so a segment cannot surface on vector similarity alone if it never says what you typed. Pass keyword_match=ranked to make it a union instead, where an unquoted keyword only boosts relevance and a strong vector match can surface without it. Quoted phrases are hard filters under both modes, so every result contains them no matter which leg it came from.

Scoping a ranked search to an entity

entity_id and company_id here are filters — they narrow ranked candidates to episodes featuring the resolved entity. The ranking still comes from semantic_search / keyword_search. To read every line about an entity, use Mentions instead.

Response

windows is bounded — never the whole segment. Each window centers on one or more high-relevance lines (flagged is_match: true) padded with surrounding context. A single segment can produce multiple non-overlapping windows when the top-scored lines are far apart inside it. When the line-scoring path can’t pinpoint a match (e.g., a degraded embedding service or no individual line scored above zero), the window falls back to the segment’s opening lines and is flagged is_preview: true. match.source is semantic, keyword, or hybrid — branch on it when rendering. clips is omitted when no highlight clip overlaps the segment. The page-level entity block appears when an entity_id or company_id filter was provided and resolved successfully — for company_id it is the company’s linked entity — and a company block additionally appears alongside it when the filter was a company_id. A reference that can’t be resolved is rejected with 422 unresolved_reference, naming the parameter and the value that failed and pointing at the endpoint that turns your text into a usable slug — an unresolvable filter is a typo to fix, not an empty result to render. A company_id that resolves to a company we hold no linked entity for is different: the request was valid and there is simply nothing to filter on, so it returns empty data and still echoes the company block (without entity) so you can render what you matched.

Filters

When a search comes back empty

An empty page is ambiguous on its own: it could mean the corpus holds nothing on your topic, or that one filter was too narrow. So when the first page of a search comes back empty and we can attribute why, the response carries a diagnostics block that says which it was. Treat it as advisory — check whether it is present rather than assuming it. It is absent whenever an empty page has nothing we can honestly attribute: paging past the end of a result set (an empty page after a cursor is ordinary exhaustion, not a filter problem), a company_id that resolves to a company with no linked entity, a language filter we cannot reproduce in the probes, and the case where ranked matches were found but dropped on the way out — a data-consistency problem on our side rather than something your request can fix. We would rather return nothing than name a filter that is not the cause.
outcome is one of: Each entry in filters reports one filter your request applied. remedy says why that filter excluded everything, and retry_with is the parameter change to apply to the same request — an empty value means remove that parameter. Where one parameter cannot be cleared on its own, retry_with names every parameter that has to change together. Entries marked emptied_results were verified by re-running your search with that one filter removed and everything else held fixed, so their retry_with is a change already known to return results rather than a guess.

Pagination

Standard limit (1–100, default 25) + opaque cursor. Pass the cursor from the previous response back as ?cursor=… to fetch the next page. Cursors are opaque — don’t parse them.