{"uid":"cap_kEO0NH_-1Tpu0a7RZcK1w","slug":"crypto-fear-greed-index-api-b12b627c","name":"Crypto Fear & Greed Index API","description":"Real-time crypto Fear & Greed index (0-100) with classification and history. Market-sentiment signal for allocation agents. Free source, deterministic. $0.005 USDC via x402 on Base. SYNTHORA. First 3 calls FREE per wallet — send header X-WALLET: 0x<addr>. No charge on upstream failure.","url":"https://fear-greed.hergertsynthora.com/service","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"input":{"type":"string","description":"SYNTHORA fear-greed: indice de miedo/codicia con la VARIACION frente a ayer y el cruce de banda, no solo el valor. Fuente: alternative.me, fechada y con hash."}}},"responseSchema":{"type":"json","example":{"ok":true,"niche":"fear_greed","result":{"senal":"el indice cambia de 'Extreme Fear' a 'Fear': giro de regimen de sentimiento","value":27,"fuente":"<omitido en el ejemplo publico>","serie_8d":[27,25,"..."],"as_of_utc":"2026-08-05T16:31:27Z","maximo_8d":29,"minimo_8d":25,"latencia_s":0.33,"delta_vs_ayer":2,"classification":"Fear","cambio_de_banda":true,"clasificacion_ayer":"Extreme Fear"}}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.05","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.05/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.05","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.05","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_vvBa55wmPJQIUfzAzmgK-","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.05","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Returns the real-time crypto Fear & Greed index (0–100) with sentiment classification and historical data points","exampleAgentPrompt":"What's the current crypto Fear & Greed index right now, and can you also give me the last 10 historical readings?","exampleUseCases":null,"resultDescription":"Returns a numeric Fear & Greed index value between 0 and 100, a human-readable sentiment classification (e.g. Extreme Fear, Fear, Neutral, Greed, Extreme Greed), and optionally a list of historical index data points up to the requested limit.","failureModes":["Upstream data source failure — no charge applied per service terms","Invalid limit parameter type returns schema validation error","Missing or malformed X-WALLET header may affect free-tier tracking","Network timeout if upstream provider is slow"],"whenToPreferThis":"Use this endpoint when an agent needs a real-time or recent-historical crypto market sentiment signal — particularly for portfolio allocation decisions, rebalancing triggers, or risk-on/risk-off logic. Prefer this over general news sentiment APIs when you need a single authoritative 0–100 index number with classification rather than raw text analysis.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T12:36:34.027Z","isFirstParty":false}