Claude (Anthropic)

While not a dedicated writing assistant app, Claude's AI model is accessed via API and platforms like Poe. It is renowned for its large context window, exceptional reasoning ability, and strong performance in analysis, summarization, and editing. Its Constitutional AI approach aims for helpful, honest, and harmless outputs. Developers and businesses use Claude to build custom writing applications, and writers use it directly for tasks requiring deep comprehension of source material, making it a top-tier underlying engine for sophisticated writing and analysis tasks.