{"slug":"what-is-the-anthropic-messages-api","verification":{"valid":true,"entries":5,"head":"19de5fa9a2bb6695cdcef2bdaa28f31e1702a043b40897a24fbcfcb68ab8d1c3"},"energy":{"passes":5,"tokens_in":0,"tokens_out":0,"tokens_total":0,"cost_usd":0,"models":{"Opus 5 (Claude Code)":5},"head":"19de5fa9a2bb6695cdcef2bdaa28f31e1702a043b40897a24fbcfcb68ab8d1c3"},"provenance":[{"ts":"2026-07-26T03:31:29.515Z","model":"Opus 5 (Claude Code)","action":"sources","prompt":"","input":"what-is-the-anthropic-messages-api","response":"4 source(s) added","tokens_in":0,"tokens_out":0,"cost":0,"prev":"genesis","hash":"e8aa8b018e109e165807af5118c0b0e6a10f5465e0184de25acc3263f68599b9"},{"ts":"2026-07-26T03:31:29.949Z","model":"Opus 5 (Claude Code)","action":"claim","prompt":"","input":"what-is-the-anthropic-messages-api c1","response":"The Anthropic Messages API is a single endpoint, POST /v1/messages, whose required fields are model, max_tokens and messages, with system instructions carried outside the turn sequence.","tokens_in":0,"tokens_out":0,"cost":0,"prev":"e8aa8b018e109e165807af5118c0b0e6a10f5465e0184de25acc3263f68599b9","hash":"2812280f3b4e8df5a0e99f3baa39d0aabbf85eac2d0585fee0328f7749c4b039"},{"ts":"2026-07-26T03:31:30.291Z","model":"Opus 5 (Claude Code)","action":"claim","prompt":"","input":"what-is-the-anthropic-messages-api c2","response":"A streamed response must emit message_start, content_block_start, content_block_delta, content_block_stop, message_delta and message_stop in that order, with tool arguments arriving as incremental input_json_delta fragments.","tokens_in":0,"tokens_out":0,"cost":0,"prev":"2812280f3b4e8df5a0e99f3baa39d0aabbf85eac2d0585fee0328f7749c4b039","hash":"0c174fea1cec4fb763af9adf0721bccf6659130a1dd3b420918e0e14305ed767"},{"ts":"2026-07-26T03:31:30.604Z","model":"Opus 5 (Claude Code)","action":"claim","prompt":"","input":"what-is-the-anthropic-messages-api c3","response":"POST /v1/messages/count_tokens is optional for a gateway: without it Claude Code estimates context locally instead of failing.","tokens_in":0,"tokens_out":0,"cost":0,"prev":"0c174fea1cec4fb763af9adf0721bccf6659130a1dd3b420918e0e14305ed767","hash":"6a3758ef876fbc0a3a19366c4c5390c2a5819e07125ac161464db4288bd372e0"},{"ts":"2026-07-26T03:31:30.982Z","model":"Opus 5 (Claude Code)","action":"claim","prompt":"","input":"what-is-the-anthropic-messages-api c4","response":"Anthropic Messages and Chat Completions differ in nine named places, and stop_sequence and cache_control have no faithful mapping between them.","tokens_in":0,"tokens_out":0,"cost":0,"prev":"6a3758ef876fbc0a3a19366c4c5390c2a5819e07125ac161464db4288bd372e0","hash":"19de5fa9a2bb6695cdcef2bdaa28f31e1702a043b40897a24fbcfcb68ab8d1c3"}]}