claude-fable-5-1

cURL

curl https://www.anyfast.ai/v1/messages \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-fable-5-1",
    "max_tokens": 4096,
    "output_config": { "effort": "high" },
    "messages": [
      { "role": "user", "content": "Identify the highest-risk assumptions in this migration plan." }
    ]
  }'

import requests

url = "https://www.anyfast.ai/v1/messages"

payload = {
    "model": "claude-fable-5-1",
    "messages": [
        {
            "role": "user",
            "content": "Identify the highest-risk assumptions in this migration plan."
        }
    ],
    "max_tokens": 4096,
    "system": "<string>",
    "metadata": { "user_id": "<string>" },
    "stop_sequences": ["<string>"],
    "stream": False,
    "tools": [
        {
            "name": "<string>",
            "input_schema": {},
            "description": "<string>"
        }
    ],
    "output_config": { "effort": "high" },
    "thinking": { "type": "adaptive" },
    "temperature": 1,
    "top_p": 1,
    "top_k": 123
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    model: 'claude-fable-5-1',
    messages: [
      {
        role: 'user',
        content: 'Identify the highest-risk assumptions in this migration plan.'
      }
    ],
    max_tokens: 4096,
    system: '<string>',
    metadata: {user_id: '<string>'},
    stop_sequences: ['<string>'],
    stream: false,
    tools: [{name: '<string>', input_schema: {}, description: '<string>'}],
    output_config: {effort: 'high'},
    thinking: {type: 'adaptive'},
    temperature: 1,
    top_p: 1,
    top_k: 123
  })
};

fetch('https://www.anyfast.ai/v1/messages', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://www.anyfast.ai/v1/messages",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'model' => 'claude-fable-5-1',
    'messages' => [
        [
                'role' => 'user',
                'content' => 'Identify the highest-risk assumptions in this migration plan.'
        ]
    ],
    'max_tokens' => 4096,
    'system' => '<string>',
    'metadata' => [
        'user_id' => '<string>'
    ],
    'stop_sequences' => [
        '<string>'
    ],
    'stream' => false,
    'tools' => [
        [
                'name' => '<string>',
                'input_schema' => [
                                
                ],
                'description' => '<string>'
        ]
    ],
    'output_config' => [
        'effort' => 'high'
    ],
    'thinking' => [
        'type' => 'adaptive'
    ],
    'temperature' => 1,
    'top_p' => 1,
    'top_k' => 123
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://www.anyfast.ai/v1/messages"

	payload := strings.NewReader("{\n  \"model\": \"claude-fable-5-1\",\n  \"messages\": [\n    {\n      \"role\": \"user\",\n      \"content\": \"Identify the highest-risk assumptions in this migration plan.\"\n    }\n  ],\n  \"max_tokens\": 4096,\n  \"system\": \"<string>\",\n  \"metadata\": {\n    \"user_id\": \"<string>\"\n  },\n  \"stop_sequences\": [\n    \"<string>\"\n  ],\n  \"stream\": false,\n  \"tools\": [\n    {\n      \"name\": \"<string>\",\n      \"input_schema\": {},\n      \"description\": \"<string>\"\n    }\n  ],\n  \"output_config\": {\n    \"effort\": \"high\"\n  },\n  \"thinking\": {\n    \"type\": \"adaptive\"\n  },\n  \"temperature\": 1,\n  \"top_p\": 1,\n  \"top_k\": 123\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://www.anyfast.ai/v1/messages")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"model\": \"claude-fable-5-1\",\n  \"messages\": [\n    {\n      \"role\": \"user\",\n      \"content\": \"Identify the highest-risk assumptions in this migration plan.\"\n    }\n  ],\n  \"max_tokens\": 4096,\n  \"system\": \"<string>\",\n  \"metadata\": {\n    \"user_id\": \"<string>\"\n  },\n  \"stop_sequences\": [\n    \"<string>\"\n  ],\n  \"stream\": false,\n  \"tools\": [\n    {\n      \"name\": \"<string>\",\n      \"input_schema\": {},\n      \"description\": \"<string>\"\n    }\n  ],\n  \"output_config\": {\n    \"effort\": \"high\"\n  },\n  \"thinking\": {\n    \"type\": \"adaptive\"\n  },\n  \"temperature\": 1,\n  \"top_p\": 1,\n  \"top_k\": 123\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://www.anyfast.ai/v1/messages")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"model\": \"claude-fable-5-1\",\n  \"messages\": [\n    {\n      \"role\": \"user\",\n      \"content\": \"Identify the highest-risk assumptions in this migration plan.\"\n    }\n  ],\n  \"max_tokens\": 4096,\n  \"system\": \"<string>\",\n  \"metadata\": {\n    \"user_id\": \"<string>\"\n  },\n  \"stop_sequences\": [\n    \"<string>\"\n  ],\n  \"stream\": false,\n  \"tools\": [\n    {\n      \"name\": \"<string>\",\n      \"input_schema\": {},\n      \"description\": \"<string>\"\n    }\n  ],\n  \"output_config\": {\n    \"effort\": \"high\"\n  },\n  \"thinking\": {\n    \"type\": \"adaptive\"\n  },\n  \"temperature\": 1,\n  \"top_p\": 1,\n  \"top_k\": 123\n}"

response = http.request(request)
puts response.read_body

{
  "id": "msg_01XFDUDYJgAACzvnptvVoYEL",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "The highest-risk assumption is that every client can tolerate the planned cutover window."
    }
  ],
  "model": "claude-fable-5-1",
  "stop_reason": "end_turn",
  "usage": {
    "input_tokens": 123,
    "output_tokens": 123,
    "cache_creation_input_tokens": 123,
    "cache_read_input_tokens": 123,
    "cache_creation": {
      "ephemeral_1h_input_tokens": 123,
      "ephemeral_5m_input_tokens": 123
    },
    "output_tokens_details": {
      "thinking_tokens": 123
    }
  },
  "stop_sequence": "<string>",
  "stop_details": {}
}

{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "Invalid request parameters"
  }
}

{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "Invalid request parameters"
  }
}

{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "Invalid request parameters"
  }
}

POST

messages

cURL

curl https://www.anyfast.ai/v1/messages \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-fable-5-1",
    "max_tokens": 4096,
    "output_config": { "effort": "high" },
    "messages": [
      { "role": "user", "content": "Identify the highest-risk assumptions in this migration plan." }
    ]
  }'

import requests

url = "https://www.anyfast.ai/v1/messages"

payload = {
    "model": "claude-fable-5-1",
    "messages": [
        {
            "role": "user",
            "content": "Identify the highest-risk assumptions in this migration plan."
        }
    ],
    "max_tokens": 4096,
    "system": "<string>",
    "metadata": { "user_id": "<string>" },
    "stop_sequences": ["<string>"],
    "stream": False,
    "tools": [
        {
            "name": "<string>",
            "input_schema": {},
            "description": "<string>"
        }
    ],
    "output_config": { "effort": "high" },
    "thinking": { "type": "adaptive" },
    "temperature": 1,
    "top_p": 1,
    "top_k": 123
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    model: 'claude-fable-5-1',
    messages: [
      {
        role: 'user',
        content: 'Identify the highest-risk assumptions in this migration plan.'
      }
    ],
    max_tokens: 4096,
    system: '<string>',
    metadata: {user_id: '<string>'},
    stop_sequences: ['<string>'],
    stream: false,
    tools: [{name: '<string>', input_schema: {}, description: '<string>'}],
    output_config: {effort: 'high'},
    thinking: {type: 'adaptive'},
    temperature: 1,
    top_p: 1,
    top_k: 123
  })
};

fetch('https://www.anyfast.ai/v1/messages', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://www.anyfast.ai/v1/messages",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'model' => 'claude-fable-5-1',
    'messages' => [
        [
                'role' => 'user',
                'content' => 'Identify the highest-risk assumptions in this migration plan.'
        ]
    ],
    'max_tokens' => 4096,
    'system' => '<string>',
    'metadata' => [
        'user_id' => '<string>'
    ],
    'stop_sequences' => [
        '<string>'
    ],
    'stream' => false,
    'tools' => [
        [
                'name' => '<string>',
                'input_schema' => [
                                
                ],
                'description' => '<string>'
        ]
    ],
    'output_config' => [
        'effort' => 'high'
    ],
    'thinking' => [
        'type' => 'adaptive'
    ],
    'temperature' => 1,
    'top_p' => 1,
    'top_k' => 123
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://www.anyfast.ai/v1/messages"

	payload := strings.NewReader("{\n  \"model\": \"claude-fable-5-1\",\n  \"messages\": [\n    {\n      \"role\": \"user\",\n      \"content\": \"Identify the highest-risk assumptions in this migration plan.\"\n    }\n  ],\n  \"max_tokens\": 4096,\n  \"system\": \"<string>\",\n  \"metadata\": {\n    \"user_id\": \"<string>\"\n  },\n  \"stop_sequences\": [\n    \"<string>\"\n  ],\n  \"stream\": false,\n  \"tools\": [\n    {\n      \"name\": \"<string>\",\n      \"input_schema\": {},\n      \"description\": \"<string>\"\n    }\n  ],\n  \"output_config\": {\n    \"effort\": \"high\"\n  },\n  \"thinking\": {\n    \"type\": \"adaptive\"\n  },\n  \"temperature\": 1,\n  \"top_p\": 1,\n  \"top_k\": 123\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://www.anyfast.ai/v1/messages")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"model\": \"claude-fable-5-1\",\n  \"messages\": [\n    {\n      \"role\": \"user\",\n      \"content\": \"Identify the highest-risk assumptions in this migration plan.\"\n    }\n  ],\n  \"max_tokens\": 4096,\n  \"system\": \"<string>\",\n  \"metadata\": {\n    \"user_id\": \"<string>\"\n  },\n  \"stop_sequences\": [\n    \"<string>\"\n  ],\n  \"stream\": false,\n  \"tools\": [\n    {\n      \"name\": \"<string>\",\n      \"input_schema\": {},\n      \"description\": \"<string>\"\n    }\n  ],\n  \"output_config\": {\n    \"effort\": \"high\"\n  },\n  \"thinking\": {\n    \"type\": \"adaptive\"\n  },\n  \"temperature\": 1,\n  \"top_p\": 1,\n  \"top_k\": 123\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://www.anyfast.ai/v1/messages")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"model\": \"claude-fable-5-1\",\n  \"messages\": [\n    {\n      \"role\": \"user\",\n      \"content\": \"Identify the highest-risk assumptions in this migration plan.\"\n    }\n  ],\n  \"max_tokens\": 4096,\n  \"system\": \"<string>\",\n  \"metadata\": {\n    \"user_id\": \"<string>\"\n  },\n  \"stop_sequences\": [\n    \"<string>\"\n  ],\n  \"stream\": false,\n  \"tools\": [\n    {\n      \"name\": \"<string>\",\n      \"input_schema\": {},\n      \"description\": \"<string>\"\n    }\n  ],\n  \"output_config\": {\n    \"effort\": \"high\"\n  },\n  \"thinking\": {\n    \"type\": \"adaptive\"\n  },\n  \"temperature\": 1,\n  \"top_p\": 1,\n  \"top_k\": 123\n}"

response = http.request(request)
puts response.read_body

{
  "id": "msg_01XFDUDYJgAACzvnptvVoYEL",
  "type": "message",
  "role": "assistant",
  "content": [
    {
      "type": "text",
      "text": "The highest-risk assumption is that every client can tolerate the planned cutover window."
    }
  ],
  "model": "claude-fable-5-1",
  "stop_reason": "end_turn",
  "usage": {
    "input_tokens": 123,
    "output_tokens": 123,
    "cache_creation_input_tokens": 123,
    "cache_read_input_tokens": 123,
    "cache_creation": {
      "ephemeral_1h_input_tokens": 123,
      "ephemeral_5m_input_tokens": 123
    },
    "output_tokens_details": {
      "thinking_tokens": 123
    }
  },
  "stop_sequence": "<string>",
  "stop_details": {}
}

{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "Invalid request parameters"
  }
}

{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "Invalid request parameters"
  }
}

{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "Invalid request parameters"
  }
}

Authorizations

Authorization

string

header

required

Bearer authentication header of the form Bearer <token>, where <token> is your auth token.

Body

application/json

model

enum<string>

required

Model ID.

Available options:

claude-fable-5-1

Example:

"claude-fable-5-1"

messages

object[]

required

Conversation turns. Pass assistant content blocks, including thinking blocks, back unchanged in multi-turn conversations. Do not prefill the final assistant response.

Minimum array length: 1

Show child attributes

Example:

[
  {
    "role": "user",
    "content": "Identify the highest-risk assumptions in this migration plan."
  }
]

max_tokens

integer

required

Maximum output tokens across thinking and visible response text.

Required range: 1 <= x <= 128000

Example:

4096

system

System prompt. Keep it byte-for-byte stable when replaying Fable 5.1 thinking blocks.

metadata

object

Request metadata.

Show child attributes

stop_sequences

string[]

Custom text sequences that stop generation.

stream

boolean

default:false

Stream message events over SSE.

tools

object[]

Tool definitions available to the model. Keep this array unchanged when replaying Fable 5.1 thinking blocks.

Show child attributes

tool_choice

object

Controls whether the model may use tools.

Show child attributes

output_config

object

Output controls. Claude Fable 5.1 defaults to high effort.

Show child attributes

thinking

object

Omit this field or use adaptive thinking. Manual enabled with budget_tokens and disabled return 400.

Show child attributes

temperature

number

default:1

deprecated

Custom temperature is unsupported. Only 1 is accepted for backward compatibility; omit this field normally.

Required range: 1 <= x <= 1

top_p

number

default:1

deprecated

Custom nucleus sampling is unsupported. Values from 0.99 to 1 are accepted only for backward compatibility; omit this field normally.

Required range: 0.99 <= x <= 1

top_k

integer

deprecated

Unsupported. Any supplied value returns 400.

Response

Message created successfully. A safety-classifier refusal is also returned with HTTP 200 and stop_reason set to refusal.

string

required

Example:

"msg_01XFDUDYJgAACzvnptvVoYEL"

type

enum<string>

required

Available options:

message

role

enum<string>

required

Available options:

assistant

content

object[]

required

Show child attributes

Example:

[
  {
    "type": "text",
    "text": "The highest-risk assumption is that every client can tolerate the planned cutover window."
  }
]

model

string

required

Example:

"claude-fable-5-1"

stop_reason

enum<string>

required

Available options:

end_turn,

max_tokens,

stop_sequence,

tool_use,

refusal,

null

usage

object

required

Show child attributes

stop_sequence

string | null

stop_details

object | null

Additional details for a refusal or other stop condition.

Overview

Native Compatible Endpoints

Model APIs

claude-fable-5-1

Authorizations

Body

Response