KeyoAPI
Claude Fable 5.1 API — Flagship Agents on a Cheap LLM API
Claude Fable 5.1 is KeyoAPI’s flagship Claude-class chat model for developers who need serious agent depth without managing a maze of vendor consoles.
Overview
Claude Fable 5.1 is KeyoAPI’s flagship Claude-class chat model for developers who need serious agent depth without managing a maze of vendor consoles. If you have been comparing claude api pricing across clouds, an AI API relay keeps the OpenAI SDK shape while letting you pick Claude when the task demands it. It suits teams that need strong coding and research quality without giving up OpenAI-compatible tooling. Fable 5.1 is positioned for long-horizon agents, complex repositories, and deep knowledge work where shallower models stall. Use it as the “planner” model in multi-agent graphs, then demote routine steps to gpt-5.6-luna or claude-sonnet-5. KeyoAPI’s relay means the same Bearer token that calls Whisper or RMBG can call Claude—useful for multimodal products that mix files, speech, and chat. Indicative Keyo sell rates for claude-fable-5-1 are about $7.35 input and $36.77 output per 1M tokens—confirm on /pricing. That is typically far below first-party Anthropic list rates for comparable flagship bands; see /compare for the current AI API price comparison tables. For budgeting, measure average input/output tokens per successful agent run rather than per message. Software teams run repo-wide refactors, migration plans, and test synthesis. Research assistants compress PDFs (often pre-parsed via MinerU2.5-Pro) into cited briefs. Support copilots escalate only the hardest tickets to Fable 5.1 while cheaper models handle FAQ deflection. Because KeyoAPI is an ai api relay, you can shadow traffic to Sonnet and measure quality before full cutover. POST to /v1/chat/completions with model claude-fable-5-1. Keep max_tokens and tool schemas identical to your OpenAI client code paths. Start at /pricing/claude-fable-5-1 to fund an account and issue a key. Treat Fable 5.1 as the planner in multi-agent graphs—long-horizon coding and research—then demote routine steps to Sonnet or Luna so token spend stays intentional. Operational tip: put Fable 5.1 behind an explicit planner queue with max tool iterations, and demote to Sonnet when the plan stabilizes. Store traces for replay. Review weekly which prompts truly needed 5.1 versus Sonnet so Claude API pricing stays intentional rather than habitual.
Quick start
Base URL: https://www.keyoapi.xyz/v1
Endpoint: POST /v1/chat/completions
Model: model=claude-fable-5-1
curl https://www.keyoapi.xyz/v1/chat/completions \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model":"claude-fable-5-1","messages":[{"role":"user","content":"Hello from KeyoAPI"}]}'Auth uses the same Bearer API key as chat. Full notes: Keyo docs.
FAQ
Why call Claude through an AI API relay?
Relays like KeyoAPI unify billing and base URL across Claude-class and GPT-class models so you can route by cost or capability without rewriting clients.
Is Claude Fable 5.1 good for coding agents?
Yes—flagship Claude-class models excel at long-horizon coding, tool use, and dense knowledge tasks. Use Sonnet variants when you need a cheaper balanced tier.