five-mcp
MCP server for the FIVE Persona Engine — an LLM persona constraint engine that generates structured JSON constraints to eliminate persona drift. Instead of describing personality in words (which LLMs interpret differently each turn), FIVE defines behavioral parameters the LLM executes as a recipe. See how it works →
Measured: with the constraint JSON + free harness, the demo character survived a 120-turn pressure test with zero persona breaks (plain prompt: 8 breaks; JSON alone: 1). Numbers, transcripts and scripts →
Free — no API key, no account.
Quick Start
Install
pip install five-mcpUse with Claude Desktop
Add to your claude_desktop_config.json:
{
"mcpServers": {
"five-character-engine": {
"command": "five-mcp"
}
}
}That's it — no environment variables needed.
Use with other MCP clients
Any MCP-compatible client can connect via stdio transport:
five-mcpTool: generate
Generates persona constraints via the FIVE engine.
Parameters
| Parameter | Type | Required | Description | |-----------|------|----------|-------------| | character_name | string | Yes | Name of the character | | q1 – q4 | A / B / C / D | Yes | Personality axis choices | | s1 – s4 | 1–5 | No | Style sliders (default: 3) | | free_text | string | No | Free-form description |
Response
{
"status": "ok",
"constraint": { "..." }
}Rate limits
The API is free. To keep it available to everyone, a light per-IP limit applies: 10 requests/min, 200 requests/day. The free host may cold-start, so the first call can take up to a minute.
Links
- API & Docs: fiveengine.dev
- GitHub: github.com/kiro0x/five-mcp
- Design philosophy & examples: five-character-engine README
- Measured evaluation (120-turn drift test): five-character-engine eval/
- Engine repo: github.com/kiro0x/five-character-engine
License
MIT
mcp-name: io.github.kiro0x/five-mcp
