Empty content array instead of empty text

[dandv]

I filed this a few months ago (#399) and it turns out it's not a Bedrock issue, and not limited to max_tokens 1.

When Claude doesn't return anything, the content array is empty. This breaks the assumption that the content array will contain an object with a text field. The correct output should be

[ { type: 'text', text: '' } ]

Repro:

import axios from 'axios';
import 'dotenv/config';

interface Message {
  role: string;
  content: string;
}

async function apiCallMessages(messages: Message[], model: string) {
  const sampleRequest = {
    messages,
    max_tokens: 4096,  // required, maximum
    model,
  };

  let parsed, response;

  response = await axios.post('https://api.anthropic.com/v1/messages', sampleRequest, {
    headers: {
      'x-api-key': process.env.ANTHROPIC_API_KEY as string,
      'anthropic-version': '2023-06-01',  // required by the Messages API, optional for Text Completions
      'anthropic-beta': 'messages-2023-12-15',  // required to use the Messages API while in beta
      'anthropic-sdk': `anthropic-sheets/0.8.1`,
    },
  }) as Record<string, string>;
  return response.data;
}

const prompt = 'Who is the best basketball player of all time? Please choose one specific player and be brief.';
let response = await apiCallMessages([
  { role: 'user', content: prompt },
  { role: 'assistant', content: 'Stephen' },
], 'claude-3-haiku-20240307');
console.log(response['content']);  // 'Curry...'

response = await apiCallMessages([
  { role: 'user', content: prompt },
  { role: 'assistant', content: 'Stephen Curry.' },
], 'claude-3-haiku-20240307');
console.log(response['content']);  // <-- [], which is an error

[rattrayalex]

Where is it documented that content should always be a non-empty array? This may be a bug in the documentation, or a misunderstanding of the API's contract.

Either way, this does not sound like a bug in the SDK, so I'm going to go ahead and close this issue.

[aaron-lerner]

When Claude doesn't return anything, the content array is empty. This breaks the assumption that the content array will contain an object with a text field. The correct output should be

[ { type: 'text', text: '' } ]

@rattrayalex is correct, that is not a valid assumption and this is the expected behavior for empty responses and matches the behavior on input where "content": [{"type": "text", "text": ""}] will give you an error.

Unrelated note:

'anthropic-beta': 'messages-2023-12-15', // required to use the Messages API while in beta

Messages API is now GA and you no longer need this header.

[dandv]

Thanks for the clarifications!