API | Claude Opus 5.5 API — Anthropic's Newest Opus, 1M Context

anthropic/claude-opus-5.5/chat

Claude Opus 5.5 chat from Anthropic, released 22 September 2026, through an OpenAI-compatible endpoint. It takes up to 1,000,000 tokens and returns up to 128,000, always thinks, offers low, medium or high effort and up to 128 tool definitions.

Input $3.60Output $18per 1 million tokensCached input $0.18Cache write $4.50Anthropic official price$4~~$20~~

Run model View API

Send a request

Examples use the selected endpoint’s public parameter definitions. Replace the API key and example media, then send the request from your server.

SDKs & integrations

POSThttps://api.spicyapi.ai/v1/chat/completions

API authentication

Keep the API key in the server environment variable SPICY_API_KEY. Use Bearer authentication and Content-Type: application/json for JSON requests.

Authorization: Bearer $SPICY_API_KEY

curl --fail-with-body -sN https://api.spicyapi.ai/v1/chat/completions \
  -H "Authorization: Bearer $SPICY_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{
  "model": "anthropic/claude-opus-5.5/chat",
  "messages": [
    {
      "role": "user",
      "content": "Summarise the following release notes into three bullet points."
    }
  ],
  "stream": true
}' \
  | jq --unbuffered -Rrj 'select(startswith("data: ")) | .[6:] | select(. != "[DONE]") | fromjson | if .error then "\n[error] \(.error.message)\n" else (.choices[0].delta.content? // empty) end'

Generated from this model’s input schema — the same one the API validates every request against.

Keep one Idempotency-Key for each logical request. After a network interruption, do not automatically resend with a new key; retain request_id to investigate the accepted request. Idempotency does not replay an earlier chat stream.

Input parameters

Place the model parameters directly in the JSON request body alongside model. This endpoint does not use an input wrapper.

messagesarray<object>Required

Ordered conversation turns. Content is a string, or an array of text and image_url parts. Put persona, setting and output format in the system message and the prior exchange after it, oldest first. The last message cannot be an assistant turn.

Default: Not specified
Constraints: minItems:1

messages[].rolestringRequired within object

Role of the message author.

Default: Not specified
Allowed values: "system""developer""user""assistant""tool"

messages[].namestringOptional

Optional name identifying the speaker within its role.

Default: Not specified

messages[].contentstring | array | nullOptional

Message content, either plain text or a list of content parts.

Default: Not specified

{
  "type": [
    "string",
    "array",
    "null"
  ],
  "items": {
    "oneOf": [
      {
        "type": "object",
        "required": [
          "type",
          "text"
        ],
        "properties": {
          "text": {
            "type": "string"
          },
          "type": {
            "const": "text"
          }
        }
      },
      {
        "type": "object",
        "required": [
          "type",
          "image_url"
        ],
        "properties": {
          "type": {
            "const": "image_url"
          },
          "image_url": {
            "type": "object",
            "required": [
              "url"
            ],
            "properties": {
              "url": {
                "type": "string"
              }
            }
          }
        }
      }
    ]
  },
  "description": "Message content, either plain text or a list of content parts."
}

messages[].tool_callsarray<object>Optional

Tool calls the assistant requested in this message.

Default: Not specified

messages[].tool_call_idstringOptional

Identifier of the tool call this message answers. Required on tool messages.

Default: Not specified

messages[].reasoning_contentstringOptional

Reasoning text from a previous assistant reply, preserved when continuing a tool conversation.

Default: Not specified

{
  "type": "array",
  "x-ui": {
    "order": 100,
    "widget": "chat-messages",
    "primary": true
  },
  "items": {
    "type": "object",
    "allOf": [
      {
        "if": {
          "required": [
            "reasoning_content"
          ]
        },
        "then": {
          "properties": {
            "role": {
              "const": "assistant"
            }
          }
        }
      }
    ],
    "required": [
      "role"
    ],
    "properties": {
      "name": {
        "type": "string",
        "description": "Optional name identifying the speaker within its role."
      },
      "role": {
        "enum": [
          "system",
          "developer",
          "user",
          "assistant",
          "tool"
        ],
        "type": "string",
        "description": "Role of the message author."
      },
      "content": {
        "type": [
          "string",
          "array",
          "null"
        ],
        "items": {
          "oneOf": [
            {
              "type": "object",
              "required": [
                "type",
                "text"
              ],
              "properties": {
                "text": {
                  "type": "string"
                },
                "type": {
                  "const": "text"
                }
              }
            },
            {
              "type": "object",
              "required": [
                "type",
                "image_url"
              ],
              "properties": {
                "type": {
                  "const": "image_url"
                },
                "image_url": {
                  "type": "object",
                  "required": [
                    "url"
                  ],
                  "properties": {
                    "url": {
                      "type": "string"
                    }
                  }
                }
              }
            }
          ]
        },
        "description": "Message content, either plain text or a list of content parts."
      },
      "tool_calls": {
        "type": "array",
        "items": {
          "type": "object"
        },
        "description": "Tool calls the assistant requested in this message."
      },
      "tool_call_id": {
        "type": "string",
        "description": "Identifier of the tool call this message answers. Required on tool messages."
      },
      "reasoning_content": {
        "type": "string",
        "description": "Reasoning text from a previous assistant reply, preserved when continuing a tool conversation."
      }
    },
    "additionalProperties": false
  },
  "minItems": 1,
  "description": "Ordered conversation turns. Text content only on this endpoint."
}

tool_choicestringOptional

auto or none. Opus 5.5 does not accept a forced tool: to get a specific call, name the tool in the prompt and leave this on auto.

Default: Not specified
Allowed values: "auto""none"

parallel_tool_callsbooleanOptional

true or false, default true: the model may request several tool calls in one turn. Set false to get at most one call per turn, for loops where each call depends on the previous result. No effect on price.

Default: true

toolsarray<object>Optional

Up to 128 function definitions per request.

Default: Not specified
Constraints: maxItems:128

stopstring | arrayOptional

Up to 4 sequences, as a string or an array. The reply ends as soon as the model writes one of them, and the matched text itself is left out. No default. It does not change the rate; a reply cut short is billed only for the tokens it produced.

Default: Not specified
Constraints: minLength:1
minItems:1
maxItems:4

reasoning_effortstringOptional

low, medium or high, medium by default - the same default Anthropic sets for this model. Thinking cannot be switched off on Opus 5.5; this only sets how much of it happens. Move to high when planted details and established facts must be reconciled before the model writes.

Default: "medium"
Allowed values: "low""medium""high"

max_tokensintegerOptional

Caps the reply at 128,000 - an eighth of the read window. Default 4,096; raise it before writing a chapter. Thinking is always on and comes out of this same budget, so a small cap can be spent on reasoning before the answer starts and come back empty or cut short - leave real room, more so when reasoning_effort is high.

Default: 4096
Constraints: minimum:1
maximum:128000

{
  "type": "object",
  "required": [
    "messages"
  ],
  "x-pricing": {
    "billingMode": "formula",
    "variantFields": []
  },
  "properties": {
    "stop": {
      "type": [
        "string",
        "array"
      ],
      "x-ui": {
        "order": 65,
        "widget": "text",
        "affects_price": false
      },
      "items": {
        "type": "string",
        "minLength": 1
      },
      "maxItems": 4,
      "minItems": 1,
      "minLength": 1,
      "description": "Sequences that end the reply as soon as the model writes one; the matched text is not returned."
    },
    "tools": {
      "type": "array",
      "x-ui": {
        "order": 35,
        "widget": "json"
      },
      "items": {
        "type": "object"
      },
      "maxItems": 128,
      "description": "Tool definitions the model may call."
    },
    "messages": {
      "type": "array",
      "x-ui": {
        "order": 100,
        "widget": "chat-messages",
        "primary": true
      },
      "items": {
        "type": "object",
        "allOf": [
          {
            "if": {
              "required": [
                "reasoning_content"
              ]
            },
            "then": {
              "properties": {
                "role": {
                  "const": "assistant"
                }
              }
            }
          }
        ],
        "required": [
          "role"
        ],
        "properties": {
          "name": {
            "type": "string",
            "description": "Optional name identifying the speaker within its role."
          },
          "role": {
            "enum": [
              "system",
              "developer",
              "user",
              "assistant",
              "tool"
            ],
            "type": "string",
            "description": "Role of the message author."
          },
          "content": {
            "type": [
              "string",
              "array",
              "null"
            ],
            "items": {
              "oneOf": [
                {
                  "type": "object",
                  "required": [
                    "type",
                    "text"
                  ],
                  "properties": {
                    "text": {
                      "type": "string"
                    },
                    "type": {
                      "const": "text"
                    }
                  }
                },
                {
                  "type": "object",
                  "required": [
                    "type",
                    "image_url"
                  ],
                  "properties": {
                    "type": {
                      "const": "image_url"
                    },
                    "image_url": {
                      "type": "object",
                      "required": [
                        "url"
                      ],
                      "properties": {
                        "url": {
                          "type": "string"
                        }
                      }
                    }
                  }
                }
              ]
            },
            "description": "Message content, either plain text or a list of content parts."
          },
          "tool_calls": {
            "type": "array",
            "items": {
              "type": "object"
            },
            "description": "Tool calls the assistant requested in this message."
          },
          "tool_call_id": {
            "type": "string",
            "description": "Identifier of the tool call this message answers. Required on tool messages."
          },
          "reasoning_content": {
            "type": "string",
            "description": "Reasoning text from a previous assistant reply, preserved when continuing a tool conversation."
          }
        },
        "additionalProperties": false
      },
      "minItems": 1,
      "description": "Ordered conversation turns. Text content only on this endpoint."
    },
    "max_tokens": {
      "type": "integer",
      "x-ui": {
        "unit": "tokens",
        "order": 80,
        "widget": "number",
        "advanced": false,
        "affects_price": false
      },
      "default": 4096,
      "maximum": 128000,
      "minimum": 1,
      "description": "Maximum number of tokens to generate in the reply."
    },
    "tool_choice": {
      "enum": [
        "auto",
        "none"
      ],
      "type": "string",
      "x-ui": {
        "order": 30,
        "widget": "text"
      },
      "description": "Whether the model may call a tool: auto or none. A forced tool call is not accepted on this model."
    },
    "reasoning_effort": {
      "enum": [
        "low",
        "medium",
        "high"
      ],
      "type": "string",
      "x-ui": {
        "order": 70,
        "widget": "radio"
      },
      "default": "medium",
      "description": "How much the model works through the task before answering."
    },
    "parallel_tool_calls": {
      "type": "boolean",
      "x-ui": {
        "order": 33,
        "widget": "switch",
        "affects_price": false
      },
      "default": true,
      "description": "Whether the model may request more than one tool call in a single turn."
    }
  },
  "x-image-token-limit": 6000,
  "x-input-token-limit": 1000000,
  "additionalProperties": false,
  "x-max-tokens-includes-reasoning": true
}

Read the result

With stream set to false, the request returns the completed chat response directly. Read choices[].message; no task polling is needed. Set stream to true when your client supports Server-Sent Events.

Completed response example

{
  "id": "chatcmpl_example",
  "object": "chat.completion",
  "created": 1788652800,
  "model": "anthropic/claude-opus-5.5/chat",
  "choices": [
    {
      "index": 0,
      "message": {
        "role": "assistant",
        "content": "Here is a concise summary of the release notes."
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 32,
    "completion_tokens": 14,
    "total_tokens": 46
  }
}

The response example is illustrative. usage reports token counts; token counts and charges depend on your actual request.

SDKs & integrations

Use SpicyAPI in your app, terminal, AI assistant or visual workflow. Choose a setup guide below.

SDKs

TypeScript · Python · Go · PHP · Java

CLI

Terminal commands and automation scripts.

MCP

Claude Code · Cursor · Codex

Agent Skill

Reusable instructions for your AI assistant.

n8n

Self-hosted community nodes and importable HTTP Request templates for n8n Cloud.

ComfyUI

Image, video and audio workflows on a node canvas.

More integrations

SillyTavern Telegram / Discord App proxy OpenAI SDK LangChain Vercel AI SDK

Browse ready-to-use workflows

This is a chat model, so it works wherever the OpenAI chat API works: keep your client, change the base URL, and select this model by its ID.

Point any OpenAI-compatible client here

export OPENAI_BASE_URL="https://api.spicyapi.ai/v1"
export OPENAI_API_KEY="$SPICY_API_KEY"

aider --model openai/anthropic/claude-opus-5.5/chat

Anything that speaks the OpenAI chat API works the same way — SDKs, the Vercel AI SDK, LangChain, aider, Cline. The MCP server and the spicyapi CLI cover asynchronous media tasks. Per-tool setup is in the developer hub.

Use it in SillyTavern and roleplay apps

In SillyTavern, RisuAI, Agnai or any app with an OpenAI-compatible setting, paste the base URL below and your API key, then pick anthropic/claude-opus-5.5/chat as the model. Browser calls are allowed, and sliders this model does not take are ignored instead of rejected.

Base URL: https://api.spicyapi.ai/v1
Model: anthropic/claude-opus-5.5/chat

SillyTavern guide RisuAI, Agnai and more SillyTavern extension

Use it in ComfyUI

Install the SpicyAPI nodes from ComfyUI Manager or with the command below, then pick anthropic/claude-opus-5.5/chat in the SpicyAPI Chat node to use this model inside a ComfyUI graph.

cd ComfyUI/custom_nodes
git clone https://github.com/spicyapi-ai/comfyui-spicyapi

Workflow examples Setup guide Source on GitHub

The embedded panel reads the same schema as this page, so it cannot drift from the API. If your docs need the content to be searchable, read the JSON under /api/embed/models/ and render it yourself.

<iframe src="https://spicyapi.ai/embed/en/models/claude-opus-5-5/api?model=anthropic%2Fclaude-opus-5.5%2Fchat" width="100%" height="560" loading="lazy" title="Request example" style="border:1px solid rgba(0,0,0,.12)"></iframe>

Open the panel

Workbench

Send a request

API authentication

Input parameters

Read the result

SDKs & integrations

Use it in SillyTavern and roleplay apps

Use it in ComfyUI