Fable MCP Server

Anthropic Claude Fable 5 MCP server — top-tier planning and code critique for handoff. That is what the fable mcp server brings to an AI assistant: the same capability, reachable through the Model Context Protocol rather than a separate app or dashboard.

The short version

An MCP (Model Context Protocol) server for Anthropic Claude Fable 5 — Anthropic's most capable, most expensive model ($10 / $50 per 1M input / output tokens, ~2× Opus). Built in Rust, it exposes Fable as specialized MCP tools (plan, critique, ask) so any MCP client can use them.

• Works everywhere MCP works — — Not limited to Claude Code. Use it in Claude Desktop, Cursor, Windsurf, custom agent frameworks, VS Code MCP extensions, scripts, or any future tool that supports the Model Context Protocol
• You control the orchestration — — Call Fable for planning or review exactly when you (or your multi-agent system) decide, instead of relying on the model to escalate
• Clean composability — — Treat Fable as a reusable specialist service alongside your other MCP servers. Perfect for modern "expensive model for judgment, cheap model for execution" workflows
• Correct Fable-specific behavior — — Proper effort levels, refusal handling (no silent fallback), long timeouts, and accurate per-call cost reporting at Fable rates

The tools it exposes

The server publishes 3 tools. What each one is for:

• plan — Flagship. Turn a goal (+ optional context) into an executor-ready implementation plan: numbered steps, exact paths/signatures, edge cases
• critique — Coverage-first review of code, a diff, or a design. Reports every finding with severity + confidence for downstream filtering. Optional focus
• ask — Raw one-shot query to Fable. Multi-turn history, system prompt, effort, optional reasoning summary

What it needs from you

• Rust (edition 2024) - An Anthropic API key from console.anthropic.com, on an org with ≥30-day data retention The server expects a config file at ~/.config/mcp-server-fable/config.toml containing at minimum your api_key. See config.toml.example. ```toml api_key = "sk-ant-..."

Getting it running

Setup follows the usual MCP pattern — install or clone the server, register it in your client's configuration file, restart the client.

How it compares

Among the developer tooling options, the useful question is rarely "what can it do" but "what does it cost you to run" — permissions, credentials, and how much of your context its toolset consumes. Fable's toolset — plan, critique, ask — is a fair guide to whether it matches your workflow. It is maintained by codeChap; worth a glance at recent repository activity before you build anything load-bearing on it.

This entry was verified against Fable's own documentation before publication; SyncDev keeps the directory reviewed rather than auto-generated.

Things to watch

• It runs with your machine's permissions. That is convenient and also the reason to think about what you point it at before you approve a tool call.
• Keep per-call confirmation enabled while you learn its behaviour; it is the cheapest safeguard you have.