struct

Anthropic::MessageCreateParams

Inherits JSON::Serializable < Struct < Value < Object

Request parameters for messages.create()

Typed struct that serializes directly to JSON for API requests. Replaces the verbose Hash(String, JSON::Any) pattern.

params = MessageCreateParams.new(
  model: "claude-sonnet-4-6",
  max_tokens: 1024,
  messages: [MessageParam.user("Hello!")],
  stream: false
)
body_json = params.to_json

Constructors

new(model : String, max_tokens : Int32, messages : Array(MessageParam), stream : Bool | Nil = nil, system : SystemPrompt | Nil = nil, temperature : Float64 | Nil = nil, top_p : Float64 | Nil = nil, top_k : Int32 | Nil = nil, tools : Array(ToolDefinition | ServerTool) | Nil = nil, tool_choice : ToolChoice | Nil = nil, stop_sequences : Array(String) | Nil = nil, metadata : Metadata | Nil = nil, service_tier : String | Nil = nil, thinking : ThinkingConfig | Nil = nil, cache_control : CacheControl | Nil = nil, container : String | Nil = nil, output_config : OutputConfig | Nil = nil, inference_geo : String | Nil = nil, fallbacks : FallbacksParam | Nil = nil, fallback_credit_token : FallbackCreditToken | Nil = nil, diagnostics : DiagnosticsParam | Nil = nil)
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new(pull : JSON::PullParser)
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new(*, __pull_for_json_serializable pull : JSON::PullParser)
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Instance methods

cache_control
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container
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diagnostics
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fallback_credit_token

Bare credit-token string or object form {token, mode}.

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fallbacks

Server-side fallback chain (Array(FallbackParam)) or "default". Requires the server-side-fallback-2026-07-01 beta (auto-attached).

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inference_geo
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max_tokens
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messages
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metadata
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model
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output_config
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service_tier
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stop_sequences
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stream
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system
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temperature
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thinking
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tool_choice
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tools
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top_k
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top_p
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