Get price history for a SINGLE asset, optimized for AI analysis

Returns ~200 intelligently sampled price data points in CSV format for any custom time range. 'slug' must be a CoinCap asset slug — resolve it first with /agentFriendly/assets_search. CoinCap slugs differ from other providers: use 'xrp' (not 'ripple'), 'render' (not 'render-token'), 'fetch' (not 'fetch-ai'), 'avalanche' (not 'avalanche-2'). Unknown slugs return HTTP 404. For MULTIPLE assets in one call (comparisons, screening, movers) use /agentFriendly/full_assets_by_slug with slugs=a,b,c and includeHistory=true; for a single current snapshot use /assets/{slug}.