YouTube Data API regionCode and relevanceLanguage parameters on search().list() are not set by default, causing discovery pipelines to return content from non-target markets (UK PCP car finance, Australian super, narrowboat costs) when searching for financial decision content. The search results look relevant by title but the underlying financial systems are country-specific and unusable for a US-focused product. No error or warning — the wrong-market content scores well on keyword matching and wastes downstream LLM probe budget.
Always pass regionCode='US' and relevanceLanguage='en' to youtube.search().list() when targeting US consumers. These are optional parameters that default to global results. Additionally, add market-awareness to your LLM evaluation prompts: include a TARGET MARKET section that instructs the model to reject content specific to non-target financial systems (UK ISAs, Australian super, UK stamp duty, etc.) unless the decision framework is universal. The YouTube API filtering reduces noise at discovery; the prompt filtering catches what slips through at evaluation.