Merge pull request 'postgres serves the store seat's verbs, databases and query, and lists its tools (ADR 0159)' (#203) from feat/postgres-serves-the-stores-verbs into main

modules/postgres/module.json

@@ -10,7 +10,11 @@
   "claims": [
     {
       "name": "mesh-store",
-      "scope": "mesh"
+      "scope": "mesh",
+      "serves": [
+        "databases",
+        "query"
+      ]
     }
   ],
   "capabilities": [

modules/postgres/tools/index.ts

@@ -33,6 +33,37 @@ export function getPostgresTools(postgres: PostgresClient): ToolDefinition[] {
   ];
 }
 
+// The store seat's verbs (novox/hq ADR 0159, 0160): the role's, not postgres's. Registered under the
+// seat's name, so the runtime serves them on the seat's subjects wherever this module holds the
+// seat and never lists them as postgres's own; scoped to what the store enables — asking what it
+// holds and reading from it — so creating a database is postgres's tool and not the store's.
+export function getStoreVerbs(postgres: PostgresClient): ToolDefinition[] {
+  return [
+    {
+      name: "databases",
+      description: "Every database the store holds, with its on-disk size.",
+      input: {},
+      run: async () => ({ databases: await postgres.listDatabases() }),
+    },
+    {
+      name: "query",
+      description: "One read-only statement against one database the store holds.",
+      input: {
+        database: { type: "string", description: "the database to query" },
+        sql: { type: "string", description: "the SELECT (or other read-only) statement" },
+      },
+      run: async (args) => {
+        const database = String(args.database ?? "");
+        const sql = String(args.sql ?? "");
+        if (!database) throw new Error("query: database is required");
+        if (!sql) throw new Error("query: sql is required");
+        const result = await postgres.readOnlyQuery(database, sql);
+        return { database, command: result.command, rows: result.rows };
+      },
+    },
+  ];
+}
+
 // The tools exist only when the server can be reached from the environment; without it, postgres
 // contributes none rather than failing the whole tool runtime.
 registerModuleTools("postgres", (env) => {
@@ -42,3 +73,11 @@ registerModuleTools("postgres", (env) => {
     return [];
   }
 });
+
+registerModuleTools("mesh-store", (env) => {
+  try {
+    return getStoreVerbs(PostgresClient.fromEnv(env));
+  } catch {
+    return [];
+  }
+});