The MCP connector
Tools & tiers
Every MCP tool sits in one of three tiers, by what the call costs. The shape isn't arbitrary — it's the whole business model in three lines.
Calliope’s MCP tools are grouped into three tiers. The tool reference lists each one; this page explains what the tiers mean and why they’re drawn where they are.
The three tiers
- Read — free. Outline, chapters, search, the Map, marginalia. Reading your book over MCP costs nothing, ever — no credits, no subscription.
- Calliope-AI — spends credits. The tools that call Calliope’s own models: entity detection, consistency checks, synopsis generation. Metered in euros on the same balance as the web app. No subscription needed.
- Write — subscription only. The tools that persist into your canon: marginalia, structure, and the Map. Available only with an active subscription. Never chapter prose.
Why it’s shaped this way
The logic is worth understanding, because it explains what you’re paying for — and what you’re not.
Reads are free because they should be. A capable client can already reason over your book from the free reads — run its own consistency pass, draft its own synopsis on its own model. Calliope neither can nor wants to stop that. Free reads are how Calliope becomes the grounding layer your agent trusts, so charging for them would be charging you to read your own book.
The value shows up when work is saved back. A synopsis your agent drafted only matters once it’s written to your outline; a fact only matters once it’s on your Map. That write — the moment your canon changes — is the moment Calliope is the source of truth, and that’s the moment worth paying for. So writing into your canon is the subscription gate. Because those writes cost Calliope essentially nothing to serve, they’re effectively unlimited under the flat fee.
Calliope’s own AI sits in the middle. Those tools cost real compute to run, so they’re metered — available to everyone, subscription or not, as a convenience rather than a moat.
The line that never moves
No tier writes your prose. There is no write_chapter_prose tool and no prose.write scope in any of the three tiers — an MCP client can tend everything around the body and never touch the body itself. That’s covered in full on the overview, and you can see the absence for yourself in the tool reference.
To let a connected client write back into your canon, unlock writes with a subscription.