anthropicUsage function

MeterUsage anthropicUsage(Map<String, Object?> response)

Anthropic Messages API usage shape: { usage: { input_tokens, output_tokens, cache_read_input_tokens, cache_creation_input_tokens } }.

Cache reads are billed at the discounted rate; cache creation is billed at full input rate (we already capture that in input_tokens).

final response = await MeteredCall.run(
  provider: 'anthropic',
  model: 'claude-sonnet-4-6',
  call: () => myAnthropicClient.messages.create(...),
  extract: (r) => anthropicUsage(r.toJson()),
);

Implementation

MeterUsage anthropicUsage(Map<String, Object?> response) {
  final Map<String, Object?>? usage = _readMap(response['usage']);
  if (usage == null) return MeterUsage.empty;
  final int input = _readInt(usage['input_tokens']) ?? 0;
  final int output = _readInt(usage['output_tokens']) ?? 0;
  final int cacheRead = _readInt(usage['cache_read_input_tokens']) ?? 0;
  return MeterUsage(
    tokensIn: input,
    tokensOut: output,
    cachedTokensIn: cacheRead,
  );
}