> For the complete documentation index, see [llms.txt](https://docs.nexos.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nexos.ai/gateway-api/messages.md).

# Messages

Anthropic-native Messages API for prompt-cache-preserving passthrough.

## Create a message (Anthropic-native)

> Anthropic-native Messages API. Accepts requests in Anthropic's wire format and forwards\
> them to the upstream Anthropic provider byte-for-byte, preserving native features such as\
> \`cache\_control\` for prompt caching. Use this endpoint when the client already speaks\
> Anthropic — it avoids the OpenAI translation layer that silently strips \`cache\_control\`.<br>

```json
{"openapi":"3.0.0","info":{"title":"Nexos AI Public API Production","version":"1.0.0"},"tags":[{"name":"Messages","description":"Anthropic-native Messages API for prompt-cache-preserving passthrough."}],"servers":[{"url":"https://api.nexos.ai"}],"security":[{"bearerAuth":[]},{"apiKeyHeader":[]}],"components":{"securitySchemes":{"bearerAuth":{"type":"http","scheme":"bearer"},"apiKeyHeader":{"type":"apiKey","in":"header","name":"X-Api-Key","description":"Authenticate by sending your nexos API key in the `X-Api-Key` header (e.g. `X-Api-Key: nexos-...` for a user key or `X-Api-Key: nexos-team-...` for a team key). This is an alternative to the `Authorization: Bearer` scheme. If both `X-Nexos-Key` and `X-Api-Key` are sent, `X-Nexos-Key` takes precedence."}},"schemas":{"CreateMessageRequest":{"type":"object","description":"Anthropic-native Messages API request body. Forwarded byte-for-byte to the upstream\nprovider — `cache_control` markers are preserved exactly where the client placed them\n(system blocks, message content blocks, tool definitions, top-level).\n","properties":{"model":{"type":"string","description":"Model identifier or alias resolved against the company's configured models. Must resolve to an Anthropic-provider model."},"messages":{"type":"array","items":{"$ref":"#/components/schemas/InputMessage"}},"system":{"description":"System prompt as a single string or as an array of text blocks (each may carry `cache_control`).","oneOf":[{"type":"string"},{"type":"array","items":{"$ref":"#/components/schemas/SystemBlock"}}]},"max_tokens":{"type":"integer","minimum":0,"description":"Maximum output tokens. Set to `0` to warm the prompt cache without generating output."},"temperature":{"type":"number","minimum":0,"maximum":1,"nullable":true,"description":"Sampling temperature. Note: the newest Claude models (Sonnet 4.6+/5) reject `temperature`, `top_p`, and `top_k` as deprecated.\n"},"top_p":{"type":"number","nullable":true,"description":"Nucleus sampling. Rejected as deprecated by the newest Claude models."},"top_k":{"type":"integer","nullable":true,"description":"Top-k sampling. Rejected as deprecated by the newest Claude models."},"stop_sequences":{"type":"array","nullable":true,"items":{"type":"string"}},"stream":{"type":"boolean","default":false,"nullable":true},"metadata":{"$ref":"#/components/schemas/Metadata","nullable":true},"tools":{"type":"array","nullable":true,"items":{"$ref":"#/components/schemas/Tool"}},"tool_choice":{"$ref":"#/components/schemas/ToolChoice","nullable":true},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true},"thinking":{"$ref":"#/components/schemas/ThinkingConfig","nullable":true},"output_config":{"$ref":"#/components/schemas/OutputConfig","nullable":true},"service_tier":{"type":"string","enum":["auto","standard_only"],"nullable":true,"description":"Anthropic API service tier. Note: models hosted on Vertex AI (currently all Claude models on the platform) reject this parameter.\n"},"container":{"type":"string","nullable":true,"description":"Container reference for code-execution tools. Note: models hosted on Vertex AI (currently all Claude models on the platform) reject this parameter.\n"}},"required":["model","messages","max_tokens"]},"InputMessage":{"type":"object","description":"A single input message in the `messages` array.","properties":{"role":{"type":"string","enum":["user","assistant"]},"content":{"description":"Either a plain string or an array of content blocks.","oneOf":[{"type":"string"},{"type":"array","items":{"$ref":"#/components/schemas/ContentBlock"}}]}},"required":["role","content"]},"ContentBlock":{"description":"A content block within a message's `content` array. Discriminator is `type`.\nStrict-typed concrete subtypes cover the full Anthropic Messages API surface;\n`cache_control` is forwarded byte-for-byte where present.\n","oneOf":[{"$ref":"#/components/schemas/TextBlock"},{"$ref":"#/components/schemas/ImageBlock"},{"$ref":"#/components/schemas/DocumentBlock"},{"$ref":"#/components/schemas/ToolUseBlock"},{"$ref":"#/components/schemas/ToolResultBlock"},{"$ref":"#/components/schemas/ThinkingBlock"},{"$ref":"#/components/schemas/RedactedThinkingBlock"},{"$ref":"#/components/schemas/ServerToolUseBlock"},{"$ref":"#/components/schemas/WebSearchToolResultBlock"},{"$ref":"#/components/schemas/SearchResultBlock"}],"discriminator":{"propertyName":"type","mapping":{"text":"#/components/schemas/TextBlock","image":"#/components/schemas/ImageBlock","document":"#/components/schemas/DocumentBlock","tool_use":"#/components/schemas/ToolUseBlock","tool_result":"#/components/schemas/ToolResultBlock","thinking":"#/components/schemas/ThinkingBlock","redacted_thinking":"#/components/schemas/RedactedThinkingBlock","server_tool_use":"#/components/schemas/ServerToolUseBlock","web_search_tool_result":"#/components/schemas/WebSearchToolResultBlock","search_result":"#/components/schemas/SearchResultBlock"}}},"TextBlock":{"type":"object","properties":{"type":{"type":"string","enum":["text"]},"text":{"type":"string"},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true},"citations":{"type":"array","nullable":true,"items":{"type":"object","properties":{"type":{"type":"string"},"cited_text":{"type":"string"},"document_index":{"type":"integer"},"document_title":{"type":"string","nullable":true},"start_char_index":{"type":"integer"},"end_char_index":{"type":"integer"},"start_page_number":{"type":"integer"},"end_page_number":{"type":"integer"},"start_block_index":{"type":"integer"},"end_block_index":{"type":"integer"}},"required":["type"]}}},"required":["type","text"]},"CacheControlEphemeral":{"type":"object","description":"Marks a caching breakpoint for prompt caching. Attach it to any cacheable element —\nsystem text blocks, message content blocks, tool definitions, `tool_use`, `tool_result`,\n`search_result`, or `document` blocks. A request may carry up to four such breakpoints.\nWhen supplied at the top level, it is automatically applied to the last cacheable block.\n","properties":{"type":{"type":"string","enum":["ephemeral"]},"ttl":{"type":"string","description":"How long the cached prefix stays valid. Omitting it falls back to `5m`; `1h` works without any beta header.","enum":["5m","1h"]}},"required":["type"]},"ImageBlock":{"type":"object","properties":{"type":{"type":"string","enum":["image"]},"source":{"$ref":"#/components/schemas/ImageSource"},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","source"]},"ImageSource":{"oneOf":[{"$ref":"#/components/schemas/ImageSourceBase64"},{"$ref":"#/components/schemas/ImageSourceURL"}]},"ImageSourceBase64":{"type":"object","properties":{"type":{"type":"string","enum":["base64"]},"media_type":{"type":"string","enum":["image/jpeg","image/png","image/gif","image/webp"]},"data":{"type":"string","description":"Base64-encoded image bytes."}},"required":["type","media_type","data"]},"ImageSourceURL":{"type":"object","properties":{"type":{"type":"string","enum":["url"]},"url":{"type":"string","format":"uri"}},"required":["type","url"]},"DocumentBlock":{"type":"object","properties":{"type":{"type":"string","enum":["document"]},"source":{"$ref":"#/components/schemas/DocumentSource"},"title":{"type":"string","nullable":true},"context":{"type":"string","nullable":true},"citations":{"$ref":"#/components/schemas/CitationsConfig","nullable":true},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","source"]},"DocumentSource":{"oneOf":[{"$ref":"#/components/schemas/DocumentSourceBase64"},{"$ref":"#/components/schemas/DocumentSourceURL"},{"$ref":"#/components/schemas/DocumentSourceText"},{"$ref":"#/components/schemas/DocumentSourceContent"}]},"DocumentSourceBase64":{"type":"object","properties":{"type":{"type":"string","enum":["base64"]},"media_type":{"type":"string","enum":["application/pdf"]},"data":{"type":"string"}},"required":["type","media_type","data"]},"DocumentSourceURL":{"type":"object","properties":{"type":{"type":"string","enum":["url"]},"url":{"type":"string","format":"uri"}},"required":["type","url"]},"DocumentSourceText":{"type":"object","properties":{"type":{"type":"string","enum":["text"]},"media_type":{"type":"string","enum":["text/plain"]},"data":{"type":"string"}},"required":["type","media_type","data"]},"DocumentSourceContent":{"type":"object","properties":{"type":{"type":"string","enum":["content"]},"content":{"type":"array","items":{"oneOf":[{"$ref":"#/components/schemas/TextBlock"},{"$ref":"#/components/schemas/ImageBlock"}]}}},"required":["type","content"]},"CitationsConfig":{"type":"object","properties":{"enabled":{"type":"boolean"}},"required":["enabled"]},"ToolUseBlock":{"type":"object","properties":{"type":{"type":"string","enum":["tool_use"]},"id":{"type":"string"},"name":{"type":"string"},"input":{"type":"object","description":"Arguments passed to the tool, matching the input schema the client declared for it."},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","id","name","input"]},"ToolResultBlock":{"type":"object","properties":{"type":{"type":"string","enum":["tool_result"]},"tool_use_id":{"type":"string"},"content":{"description":"Either a plain string or an array of text/image content blocks.","oneOf":[{"type":"string"},{"type":"array","items":{"oneOf":[{"$ref":"#/components/schemas/TextBlock"},{"$ref":"#/components/schemas/ImageBlock"}]}}]},"is_error":{"type":"boolean","nullable":true},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","tool_use_id"]},"ThinkingBlock":{"type":"object","properties":{"type":{"type":"string","enum":["thinking"]},"thinking":{"type":"string"},"signature":{"type":"string"},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","thinking","signature"]},"RedactedThinkingBlock":{"type":"object","properties":{"type":{"type":"string","enum":["redacted_thinking"]},"data":{"type":"string"}},"required":["type","data"]},"ServerToolUseBlock":{"type":"object","description":"A built-in tool call (such as `web_search` or `code_execution`) that the provider runs on its own side.","properties":{"type":{"type":"string","enum":["server_tool_use"]},"id":{"type":"string"},"name":{"type":"string"},"input":{"type":"object"},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","id","name","input"]},"WebSearchToolResultBlock":{"type":"object","properties":{"type":{"type":"string","enum":["web_search_tool_result"]},"tool_use_id":{"type":"string"},"content":{"description":"Either an array of search results or an error block.","oneOf":[{"type":"array","items":{"type":"object","properties":{"type":{"type":"string","enum":["web_search_result"]},"url":{"type":"string"},"title":{"type":"string"},"encrypted_content":{"type":"string"},"page_age":{"type":"string","nullable":true}},"required":["type","url","title","encrypted_content"]}},{"type":"object","properties":{"type":{"type":"string","enum":["web_search_tool_result_error"]},"error_code":{"type":"string"}},"required":["type","error_code"]}]},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","tool_use_id","content"]},"SearchResultBlock":{"type":"object","properties":{"type":{"type":"string","enum":["search_result"]},"source":{"type":"string","nullable":true},"title":{"type":"string","nullable":true},"content":{"type":"array","items":{"$ref":"#/components/schemas/TextBlock"}},"citations":{"$ref":"#/components/schemas/CitationsConfig","nullable":true},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","content"]},"SystemBlock":{"type":"object","description":"A system prompt content block. Supports `cache_control` for caching the system prefix.","properties":{"type":{"type":"string","enum":["text"]},"text":{"type":"string"},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","text"]},"Metadata":{"type":"object","description":"Optional request metadata passed through to the provider. The `user_id` field helps the provider associate the request with an end user.","properties":{"user_id":{"type":"string","nullable":true}}},"Tool":{"description":"Tool definition. Either a custom tool (function with input_schema) or a built-in server tool (typed by versioned `type`).","oneOf":[{"$ref":"#/components/schemas/CustomTool"},{"$ref":"#/components/schemas/ServerTool"}]},"CustomTool":{"type":"object","description":"A function tool that the client defines and implements.","properties":{"name":{"type":"string"},"description":{"type":"string"},"input_schema":{"type":"object","description":"A JSON Schema object that defines the shape of the tool's input arguments."},"type":{"type":"string","enum":["custom"],"description":"Optional type marker. Leave it out for legacy custom tools, or set it to `custom` when you need to be explicit."},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["name","input_schema"]},"ServerTool":{"type":"object","description":"A provider-hosted built-in tool, identified by its versioned type (for example `web_search_20250305`, `code_execution_20250825`, `bash_20250124`, `text_editor_20250124`, or `memory_20250818`).","properties":{"type":{"type":"string"},"name":{"type":"string"},"cache_control":{"$ref":"#/components/schemas/CacheControlEphemeral","nullable":true}},"required":["type","name"]},"ToolChoice":{"description":"Controls how the model selects tools.","oneOf":[{"$ref":"#/components/schemas/ToolChoiceAuto"},{"$ref":"#/components/schemas/ToolChoiceAny"},{"$ref":"#/components/schemas/ToolChoiceTool"},{"$ref":"#/components/schemas/ToolChoiceNone"}],"discriminator":{"propertyName":"type","mapping":{"auto":"#/components/schemas/ToolChoiceAuto","any":"#/components/schemas/ToolChoiceAny","tool":"#/components/schemas/ToolChoiceTool","none":"#/components/schemas/ToolChoiceNone"}}},"ToolChoiceAuto":{"type":"object","properties":{"type":{"type":"string","enum":["auto"]},"disable_parallel_tool_use":{"type":"boolean","nullable":true}},"required":["type"]},"ToolChoiceAny":{"type":"object","properties":{"type":{"type":"string","enum":["any"]},"disable_parallel_tool_use":{"type":"boolean","nullable":true}},"required":["type"]},"ToolChoiceTool":{"type":"object","properties":{"type":{"type":"string","enum":["tool"]},"name":{"type":"string"},"disable_parallel_tool_use":{"type":"boolean","nullable":true}},"required":["type","name"]},"ToolChoiceNone":{"type":"object","properties":{"type":{"type":"string","enum":["none"]}},"required":["type"]},"ThinkingConfig":{"description":"Extended thinking configuration.","oneOf":[{"$ref":"#/components/schemas/EnabledThinkingConfig"},{"$ref":"#/components/schemas/AdaptiveThinkingConfig"},{"$ref":"#/components/schemas/DisabledThinkingConfig"}],"discriminator":{"propertyName":"type","mapping":{"enabled":"#/components/schemas/EnabledThinkingConfig","adaptive":"#/components/schemas/AdaptiveThinkingConfig","disabled":"#/components/schemas/DisabledThinkingConfig"}}},"EnabledThinkingConfig":{"type":"object","description":"Manual thinking budget. Supported by Claude 4.x and older models; Claude 5 models reject this form — use `AdaptiveThinkingConfig` with `output_config.effort` instead.\n","properties":{"type":{"type":"string","enum":["enabled"]},"budget_tokens":{"type":"integer","minimum":1024}},"required":["type","budget_tokens"]},"AdaptiveThinkingConfig":{"type":"object","description":"Adaptive thinking — the model decides how much to think based on the request. Required form for Claude 5 models (which reject `enabled`/`budget_tokens`). Tune the thinking depth with the top-level `output_config.effort` parameter.\n","properties":{"type":{"type":"string","enum":["adaptive"]}},"required":["type"]},"DisabledThinkingConfig":{"type":"object","properties":{"type":{"type":"string","enum":["disabled"]}},"required":["type"]},"OutputConfig":{"type":"object","description":"Output configuration. Controls how much effort the model puts into the response when adaptive thinking is enabled.\n","properties":{"effort":{"type":"string","description":"Effort level applied when `thinking.type` is `adaptive`.","enum":["low","medium","high"]}}},"MessagesResponse":{"type":"object","description":"Anthropic-native non-streaming Messages API response.","properties":{"id":{"type":"string"},"type":{"type":"string","enum":["message"]},"role":{"type":"string","enum":["assistant"]},"model":{"type":"string"},"content":{"type":"array","items":{"$ref":"#/components/schemas/ContentBlock"}},"stop_reason":{"type":"string","nullable":true,"enum":["end_turn","max_tokens","stop_sequence","tool_use","pause_turn","refusal"]},"stop_sequence":{"type":"string","nullable":true},"stop_details":{"type":"object","nullable":true,"description":"Additional details about why the model stopped, when available."},"usage":{"$ref":"#/components/schemas/Usage"},"container":{"$ref":"#/components/schemas/Container","nullable":true}},"required":["id","type","role","content","model","usage"]},"Usage":{"type":"object","description":"Token counts reported for the request.","properties":{"input_tokens":{"type":"integer","description":"Number of input tokens charged for the request, not counting any tokens read from cache."},"output_tokens":{"type":"integer"},"cache_creation_input_tokens":{"type":"integer","nullable":true,"description":"Number of input tokens stored into the prompt cache during this request."},"cache_read_input_tokens":{"type":"integer","nullable":true,"description":"Number of input tokens read back from the prompt cache, which are billed at a reduced rate."},"cache_creation":{"$ref":"#/components/schemas/CacheCreation","nullable":true},"output_tokens_details":{"type":"object","nullable":true,"description":"Breakdown of the output tokens.","properties":{"thinking_tokens":{"type":"integer","description":"Number of output tokens used for extended thinking."}}},"service_tier":{"type":"string","nullable":true},"server_tool_use":{"$ref":"#/components/schemas/ServerToolUsage","nullable":true},"nexos_credits_cost":{"type":"number","format":"double","description":"Cost of the request in nexos credits."}},"required":["input_tokens","output_tokens"]},"CacheCreation":{"type":"object","description":"Breakdown of cache-write tokens split by cache lifetime tier.","properties":{"ephemeral_5m_input_tokens":{"type":"integer"},"ephemeral_1h_input_tokens":{"type":"integer"}}},"ServerToolUsage":{"type":"object","description":"Usage counts for each server-side tool, present when those tools ran during the request.","properties":{"web_search_requests":{"type":"integer"}}},"Container":{"type":"object","description":"Details of the execution container, included when the request used server-side code execution.","properties":{"id":{"type":"string"},"expires_at":{"type":"string","format":"date-time"}},"required":["id","expires_at"]},"MessagesStreamEvent":{"description":"Anthropic-native Messages API SSE event. Discriminated by `type`. Forwarded byte-for-byte\nfrom the upstream provider — public-api does not transform individual events.\n","oneOf":[{"$ref":"#/components/schemas/MessageStartEvent"},{"$ref":"#/components/schemas/ContentBlockStartEvent"},{"$ref":"#/components/schemas/ContentBlockDeltaEvent"},{"$ref":"#/components/schemas/ContentBlockStopEvent"},{"$ref":"#/components/schemas/MessageDeltaEvent"},{"$ref":"#/components/schemas/MessageStopEvent"},{"$ref":"#/components/schemas/PingEvent"},{"$ref":"#/components/schemas/ErrorEvent"}],"discriminator":{"propertyName":"type","mapping":{"message_start":"#/components/schemas/MessageStartEvent","content_block_start":"#/components/schemas/ContentBlockStartEvent","content_block_delta":"#/components/schemas/ContentBlockDeltaEvent","content_block_stop":"#/components/schemas/ContentBlockStopEvent","message_delta":"#/components/schemas/MessageDeltaEvent","message_stop":"#/components/schemas/MessageStopEvent","ping":"#/components/schemas/PingEvent","error":"#/components/schemas/ErrorEvent"}}},"MessageStartEvent":{"type":"object","properties":{"type":{"type":"string","enum":["message_start"]},"message":{"$ref":"#/components/schemas/MessagesResponse"}},"required":["type","message"]},"ContentBlockStartEvent":{"type":"object","properties":{"type":{"type":"string","enum":["content_block_start"]},"index":{"type":"integer"},"content_block":{"$ref":"#/components/schemas/ContentBlock"}},"required":["type","index","content_block"]},"ContentBlockDeltaEvent":{"type":"object","properties":{"type":{"type":"string","enum":["content_block_delta"]},"index":{"type":"integer"},"delta":{"$ref":"#/components/schemas/ContentBlockDelta"}},"required":["type","index","delta"]},"ContentBlockDelta":{"oneOf":[{"$ref":"#/components/schemas/TextDelta"},{"$ref":"#/components/schemas/InputJsonDelta"},{"$ref":"#/components/schemas/ThinkingDelta"},{"$ref":"#/components/schemas/SignatureDelta"},{"$ref":"#/components/schemas/CitationsDelta"}],"discriminator":{"propertyName":"type","mapping":{"text_delta":"#/components/schemas/TextDelta","input_json_delta":"#/components/schemas/InputJsonDelta","thinking_delta":"#/components/schemas/ThinkingDelta","signature_delta":"#/components/schemas/SignatureDelta","citations_delta":"#/components/schemas/CitationsDelta"}}},"TextDelta":{"type":"object","properties":{"type":{"type":"string","enum":["text_delta"]},"text":{"type":"string"}},"required":["type","text"]},"InputJsonDelta":{"type":"object","properties":{"type":{"type":"string","enum":["input_json_delta"]},"partial_json":{"type":"string"}},"required":["type","partial_json"]},"ThinkingDelta":{"type":"object","properties":{"type":{"type":"string","enum":["thinking_delta"]},"thinking":{"type":"string"}},"required":["type","thinking"]},"SignatureDelta":{"type":"object","properties":{"type":{"type":"string","enum":["signature_delta"]},"signature":{"type":"string"}},"required":["type","signature"]},"CitationsDelta":{"type":"object","properties":{"type":{"type":"string","enum":["citations_delta"]},"citation":{"type":"object","properties":{"type":{"type":"string"}},"required":["type"]}},"required":["type","citation"]},"ContentBlockStopEvent":{"type":"object","properties":{"type":{"type":"string","enum":["content_block_stop"]},"index":{"type":"integer"}},"required":["type","index"]},"MessageDeltaEvent":{"type":"object","properties":{"type":{"type":"string","enum":["message_delta"]},"delta":{"$ref":"#/components/schemas/MessageDelta"},"usage":{"$ref":"#/components/schemas/Usage"}},"required":["type","delta","usage"]},"MessageDelta":{"type":"object","description":"Top-level message delta carrying terminal stop_reason / stop_sequence.","properties":{"stop_reason":{"type":"string","nullable":true,"enum":["end_turn","max_tokens","stop_sequence","tool_use","pause_turn","refusal"]},"stop_sequence":{"type":"string","nullable":true}}},"MessageStopEvent":{"type":"object","properties":{"type":{"type":"string","enum":["message_stop"]}},"required":["type"]},"PingEvent":{"type":"object","properties":{"type":{"type":"string","enum":["ping"]}},"required":["type"]},"ErrorEvent":{"type":"object","properties":{"type":{"type":"string","enum":["error"]},"error":{"type":"object","properties":{"type":{"type":"string"},"message":{"type":"string"}},"required":["type","message"]}},"required":["type","error"]}}},"paths":{"/v1/messages":{"post":{"operationId":"createMessage","tags":["Messages"],"summary":"Create a message (Anthropic-native)","description":"Anthropic-native Messages API. Accepts requests in Anthropic's wire format and forwards\nthem to the upstream Anthropic provider byte-for-byte, preserving native features such as\n`cache_control` for prompt caching. Use this endpoint when the client already speaks\nAnthropic — it avoids the OpenAI translation layer that silently strips `cache_control`.\n","requestBody":{"required":true,"content":{"application/json":{"schema":{"$ref":"#/components/schemas/CreateMessageRequest"}}}},"responses":{"200":{"description":"OK","content":{"application/json":{"schema":{"$ref":"#/components/schemas/MessagesResponse"}},"text/event-stream":{"schema":{"$ref":"#/components/schemas/MessagesStreamEvent"}}}}}}}}}
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.nexos.ai/gateway-api/messages.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.