{"uid":"cap_9qezLA2eU4ECnv1uSj2yw","slug":"singit-ask-anthropic-messages-api-1c1f8c1d","name":"SingIt Ask – Anthropic Messages API","description":"SingIt Ask: Anthropic's Messages API (what Claude Code and the Anthropic SDK speak), any model listed at GET /v1/models, Claude included. Call it when an agent needs a Claude-format answer with no API key or account, or wants to try another model the same way.","url":"https://ask.singitai.app/v1/messages?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"model":{"type":"string","examples":["claude-sonnet-5.5","gpt-5.5","gemini-3.1-pro"],"maxLength":120,"description":"Any model id from GET /v1/models; Anthropic's dashed names (claude-sonnet-5-5) work too."},"tools":{"type":"array","description":"Optional Anthropic tool definitions."},"stream":{"enum":[false],"type":"boolean","description":"Streaming is not offered: an answer is paid for whole."},"system":{"description":"Optional system-level context for the model, as text or content blocks."},"messages":{"type":"array","items":{"type":"object","required":["role","content"],"properties":{"role":{"enum":["user","assistant"],"type":"string"},"content":{"description":"Text, or a list of Anthropic content blocks."}}},"maxItems":200,"minItems":1,"description":"The conversation, oldest first (Anthropic format)."},"max_tokens":{"type":"integer","maximum":32000,"minimum":1,"description":"The longest answer, in tokens. The payment ceiling grows with it; the charge follows what was used."}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.0015","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":"$0.003/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.003","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.003","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_LE96MF4wcKQ4LhHImZWzk","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.003","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Sends a prompt to Claude or any listed model via Anthropic's Messages API, paying per successful answer in USDC over x402 with no account or API key required.","exampleAgentPrompt":"Ask Claude to explain the pros and cons of transformer architectures versus state space models in about three paragraphs — no API key needed, just pay per answer.","exampleUseCases":[{"title":"Ad-hoc Claude reasoning without subscription","prompt":"I need Claude to analyze this contract clause and flag any ambiguous liability language — I don't have an Anthropic account, just pay per answer in USDC."},{"title":"Automated document summarization pipeline","prompt":"Summarize each of these 10 research abstracts into two sentences each using Claude, billing in USDC on Base so I don't need to manage API keys or quotas."},{"title":"Coding help via crypto-native agent","prompt":"Ask Claude to write a Python function that parses nested JSON into a flat dictionary with dot-notation keys, and pay for it from my Base wallet."}],"resultDescription":"Returns an Anthropic Messages API-compatible JSON response containing the assistant's generated message content, stop reason, model used, and token usage counts. Charged only when a valid answer is delivered; the charge is actual token cost plus 30% plus a small settlement fee (0.001 USDC on Base, 0.002 on Solana), up to a per-request ceiling.","failureModes":["Payment not received or insufficient funds — request rejected before inference","Model not found in /v1/models list — returns 404 or 400","Malformed request body (missing required fields) — 422 validation error","Upstream Anthropic API error — proxied error response with no charge","Request too large for model context window — error with no charge","Network timeout on slow requests — may require retry"],"whenToPreferThis":"Choose this endpoint when you need Anthropic Messages API compatibility (Claude models) specifically, want to pay per successful answer rather than via subscription, and are operating in a crypto-native or x402-capable agent environment. Prefer the sibling OpenAI Responses API endpoint if you need GPT or Gemini models instead. Best for agents that lack Anthropic API credentials or need to avoid recurring billing.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-28T12:35:11.946Z","isFirstParty":false,"canonicalSlug":"singit-ask-anthropic-messages-api-1c1f8c1d"}