service-ize

README.md

@@ -83,7 +83,11 @@ Handlers return plain data (`(tbd.http/respond 200 {:result 5})`), and the muunt
 
 Each logged-in user has their own todo list, keyed by their Gitea user id. Every query is
 filtered by that id, so users can't see or change each other's todos; someone else's todo answers
-`404`, exactly like a missing one. Without a login the todo routes answer `401`.
+`404`, exactly like a missing one. Without a login the todo routes answer `401`. The operations
+themselves (ownership, validation, storage) live in `src/tbd/todo/service.clj`, which the HTTP routes
+and the [MCP tools](#mcp-server) both call, so they behave the same and are tested once; a route or
+tool only translates its request into a service call and the result into a response, and never
+touches the database.
 
 Todos are stored in a local [SQLite](https://www.sqlite.org/) file, `data/todo.db` by default
 (git-ignored), which is created and migrated on the first todo request. Set `TODO_DB_PATH` to put it
@@ -117,7 +121,9 @@ be the address the client uses; without them `/mcp` answers `503` rather than be
 It offers these tools: `ping`, `add` (the same logic as `/api/add`), `whoami` (which user this
 connection acts as, and whether they are an admin), and, on the caller's own todos (the same ones
 as `/api/todos`), `list_todos`, `get_todo`, `create_todo`, `update_todo` and `delete_todo`. To add a
-tool, add a `tool` to `src/tbd/mcp/tools.clj`. Its arguments are described by the group's
+tool, add a `tool` to `src/tbd/mcp/tools.clj`; it should call the group's service (or pure `core`
+functions), not a database, and if the group has no service yet, that is the thing to add, so the
+HTTP routes can share it. Its arguments are described by the group's
 [Malli](https://github.com/metosin/malli) schema in `src/tbd/<group>/schema.clj`, the same schema the
 HTTP routes use for their parameters, so a shape of data is written down once: the tool's
 input schema is generated from it, and the arguments a client sends are coerced and validated against