Developer Overview
Clocktower is a subscription protocol on EVM chains.
If you are building an app, backend, or AI agent that needs to work with recurring payments, subscriber accounts, or protocol data, you do not have to stitch everything together from raw contract calls alone.
We provide two HTTP surfaces:
- REST API (
api.clocktower.finance) — query subscriptions, accounts, and history on a selected protocol chain; prepare transactions your users sign in their own wallet. - MCP server (
mcp.clocktower.finance) — the same capabilities exposed as tools for AI agents and MCP clients, using the same free and developer access as REST.
These surfaces answer the same kinds of questions: Who is subscribed to what? What is due next? How do I create a transaction that subscribes? What transaction should the user sign?
Hosted REST and MCP usage is governed by the Terms of Use.
What you can build
With REST, you can power dashboards, backends, and browser apps: look up providers and subscribers, inspect payment history, check whether a subscription is ready to process, and get prepared calldata for creates, updates, cancels, and remits. Your app prepares; the user signs.
With MCP, you can let an agent reason over live protocol state: discover subscriptions, inspect accounts, and request prepared writes through standard MCP tools. Access uses the same free rate limits and optional developer API keys as REST — a good fit when the caller is an agent rather than your own server.
(REST defaults to Base (chainId 8453) and accepts optional ?chainId= on protocol routes. MCP tools take optional chainId and default to Base.)
Choose your integration path
| Surface | Best for | Auth | Writes |
|---|---|---|---|
| REST API | Backends, scripts, browser apps (with CORS) | Free (IP), developer API key (ctk_…) | Prepare-only — sign in wallet; tight prepare caps |
| MCP Server | AI agents and MCP clients | Free (IP), developer API key (ctk_…) — same as REST | Prepare-only — sign in wallet |
For raw on-chain contract structs and function signatures, see the Contract Technical Reference.
Access tiers
| Lane | Surface | Auth | Default limits (approx.) |
|---|---|---|---|
| Free | REST and MCP | None (IP) | 20 rpm; expensive 3 rpm; subgraph 100/day; prepare 2/min · 20/day; 500 req/day |
| Developer | REST and MCP | Authorization: Bearer ctk_… | 80 rpm; expensive 40; subgraph 3k/day; prepare 5/min · 100/day; 5k req/day |
- Free — try without signup; highly metered.
- Developer — free API key for integrators; higher read limits. Prepare stays intentionally tight (simulation costs shared RPC). Mint keys at developers.clocktower.finance.
- MCP — same free and developer credentials and limits as REST; send
ctk_…asAuthorizationon the MCP connection.
See GET /catalog on api.clocktower.finance for the live tier manifest (writeRpm, writeDaily, dailyTotalRequests, developerKeysEnabled) and the chains[] registry. REST chain selection: Chain selection.
Write model (prepare-only)
Neither REST nor MCP sends transactions for you. Every write follows:
check readiness (optional) → prepare → sign in wallet → broadcast → poll status (optional)
Prefer by-id prepare/readiness routes when you already have a subscription id (prepare/subscribe_by_id, etc.).
Next steps
Source repositories
| Repo | Description |
|---|---|
| clocktower-api | REST and MCP server |
| clocktower-agent | CLI for testing REST and MCP |