src/client.ts

@@ -40,6 +40,9 @@ export interface Tool {
   input?: unknown;
   /** True for a role's tool: addressed to the seat, answered by whoever holds it (ADR 0132). */
   seat?: boolean;
+  /** A role's scope: `node` for a seat held once per machine, whose verb is asked of one machine
+   *  (design 33 §4) and takes `node` for it; `mesh` or absent otherwise. */
+  scope?: string;
   /** Where the tool is answered, as the mesh issued it (ADR 0160): the plain subject first when the
    *  module answers for itself anywhere, then one per machine. Absent for a runtime older than this. */
   subjects?: string[];
@@ -177,11 +180,11 @@ export async function toolsOn(bus: Broker): Promise<Listing> {
   const notAnswering: string[] = [];
   if (roles) {
     for (const s of roles.seats ?? []) {
-      // A node-scoped seat's tool is asked of one machine, and the listing does not know which;
-      // those wait for a caller naming the node (`seat:<seat>.<verb>@<node>`).
-      if (s.scope === "node") continue;
+      // A node-scoped seat's tool is asked of one machine (design 33 §4): listed with its scope, so
+      // a caller names the machine and the call carries it — `seat:<seat>.<verb>@<node>`. Left out
+      // of the listing, the verb never resolved as a seat's and nothing served it (ADR 0169).
       for (const t of s.tools ?? []) {
-        tools.push({ module: s.seat, name: t.name, description: t.description, input: t.input, seat: true });
+        tools.push({ module: s.seat, name: t.name, description: t.description, input: t.input, seat: true, scope: s.scope });
       }
     }
   } else {

src/mcp.ts

@@ -122,7 +122,9 @@ export function mcpSurface(bus: Broker, who: string): Surface {
               // the module runs on several (novox/hq ADR 0159); a seat's verb takes none, the
               // seat's scope decides. An empty object is a tool that takes nothing, which is a
               // real answer and not a missing one.
-              inputSchema: t.seat ? asSchema(t.input) : withNode(asSchema(t.input)),
+              inputSchema: t.seat && t.scope !== "node" ? asSchema(t.input)
+                : t.seat ? withNode(asSchema(t.input), "the machine whose seat answers; required, the seat is held once per machine", true)
+                : withNode(asSchema(t.input)),
             })),
             // Silence, named (design 34 §3): the modules the catalogue holds and nothing answered
             // for. Not a tool, so not in `tools`; not dropped either.
@@ -139,9 +141,18 @@ export function mcpSurface(bus: Broker, who: string): Surface {
           // is the verb's own, as `push` and `assign` take one, and is handed through untouched.
           const have = await listing().catch(() => undefined);
           const roles = have && seatsIn(have);
-          const isSeatVerb = roles ? toolKey(given.split("@", 1)[0], roles).startsWith("seat:") : false;
-          const node = !isSeatVerb && typeof args.node === "string" && args.node !== "" ? args.node : "";
-          if (!isSeatVerb) delete args.node;
+          const bare = given.split("@", 1)[0];
+          const isSeatVerb = roles ? toolKey(bare, roles).startsWith("seat:") : false;
+          // A node-scoped seat's verb is asked of one machine (design 33 §4, ADR 0169): `node`
+          // names it and travels in the subject, as for a module's tool.
+          const nodeScoped = isSeatVerb && (have?.tools.some((t) => t.seat && t.scope === "node" &&
+            `${t.module}.${t.name}` === bare) ?? false);
+          const takesNode = !isSeatVerb || nodeScoped;
+          const node = takesNode && typeof args.node === "string" && args.node !== "" ? args.node : "";
+          if (takesNode) delete args.node;
+          if (nodeScoped && !node && !given.includes("@")) {
+            return refuse(request.id, -32602, `${given} is a machine's seat's verb: name the machine with \`node\``);
+          }
           const name = node && !given.includes("@") ? `${given}@${node}` : given;
           try {
             const { result, node: answeredBy } = await callTool(bus, name, args, roles, have);
@@ -229,13 +240,19 @@ async function* lines(): AsyncGenerator<string> {
 
 /** Every module tool takes an optional `node`: the machine to ask when the module runs on several
  *  (novox/hq ADR 0159). Added to the listing, stripped before the call, never seen by the module. */
-function withNode(schema: Record<string, unknown>): Record<string, unknown> {
+function withNode(schema: Record<string, unknown>, description?: string, required = false): Record<string, unknown> {
   const properties = { ...((schema.properties as Record<string, unknown> | undefined) ?? {}) };
   if (!("node" in properties)) {
     properties.node = {
       type: "string",
-      description: "the machine to ask, when this module runs on several; else whichever answers, and the answer says which",
+      description: description ??
+        "the machine to ask, when this module runs on several; else whichever answers, and the answer says which",
     };
   }
-  return { ...schema, type: "object", properties };
+  const out: Record<string, unknown> = { ...schema, type: "object", properties };
+  if (required) {
+    const have = Array.isArray(schema.required) ? (schema.required as string[]) : [];
+    out.required = have.includes("node") ? have : [...have, "node"];
+  }
+  return out;
 }

test/client.test.ts

@@ -14,7 +14,7 @@ import { test } from "node:test";
 // The built output, not the source: the client imports its siblings as `.js`, which is what ships and
 // what every other file here does, and cannot be loaded as TypeScript directly. `pretest` builds.
 import { connectNats } from "../dist/broker-nats.js";
-import { callTool, toolsOn, whyItFailed } from "../dist/client.js";
+import { callTool, seatsIn, toolKey, toolsOn, whyItFailed } from "../dist/client.js";
 
 const url = process.env.MESH_TEST_NATS;
 
@@ -64,12 +64,15 @@ test("a person sees what the running modules answer, sorted, and who did not ans
     const have = await toolsOn(person);
     assert.deepEqual(
       have.tools.map((x) => `${x.module}.${x.name}`),
-      ["mesh-catalog.catalog_modules", "mesh-controller.status", "shop.price"],
+      ["mesh-catalog.catalog_modules", "mesh-controller.status", "node-dns-resolver.lookup", "shop.price"],
       "the list is what the modules answered plus every role's tools, in a stable order",
     );
-    // A role's tool is marked as one; a node-scoped seat's waits for a caller naming the node.
+    // A role's tool is marked as one; a node-scoped seat's carries its scope, so a caller names
+    // the machine and the verb resolves as the seat's (design 33 §4, ADR 0169).
     assert.ok(have.tools.find((x) => x.module === "mesh-controller")!.seat);
-    assert.ok(!have.tools.some((x) => x.module === "node-dns-resolver"));
+    const lookup = have.tools.find((x) => x.module === "node-dns-resolver")!;
+    assert.ok(lookup.seat && lookup.scope === "node");
+    assert.equal(toolKey("node-dns-resolver.lookup", seatsIn(have)), "seat:node-dns-resolver.lookup");
     // Silence is named, never dropped: a module the catalogue holds and nothing answered for.
     assert.deepEqual(have.notAnswering, ["ghost"]);
     // And at once: a module that is not running costs nothing, or the list is unusable.

test/mcp.test.ts

@@ -30,11 +30,16 @@ async function aMeshAndACredential(t: { after: (fn: () => Promise<void> | void)
   await shop.handle("price", async (body: { of?: string }) => ({ of: body.of ?? "nothing", cost: 12 }));
   const controller = await connectNats({ url: url!, module: "mesh-controller" });
   await controller.handle("seat:mesh-controller.tools", async () => ({
-    seats: [{ seat: "mesh-controller", scope: "mesh", tools: [
-      { name: "status", description: "what is wrong", input: {} },
-      { name: "push", description: "tell a machine", input: { node: { type: "string" } } },
-    ] }],
+    seats: [
+      { seat: "mesh-controller", scope: "mesh", tools: [
+        { name: "status", description: "what is wrong", input: {} },
+        { name: "push", description: "tell a machine", input: { node: { type: "string" } } },
+      ] },
+      // A seat held once per machine (design 33 §4, ADR 0169): its verb is asked of one.
+      { seat: "node-dns-resolver", scope: "node", tools: [{ name: "lookup", description: "one machine's", input: {} }] },
+    ],
   }));
+  await controller.handle("seat:node-dns-resolver.lookup@anchor", async () => ({ machine: "anchor", answered: true }));
   await controller.handle("seat:mesh-controller.status", async () => ({ output: "all quiet", ok: true }));
   await controller.handle("seat:mesh-controller.push", async (body: { node?: string }) => ({ told: body.node ?? "nobody" }));
   t.after(async () => {
@@ -99,9 +104,14 @@ test("a host initialises, lists the mesh's tools and calls one", async (t) => {
   assert.match(hello.instructions, /ada/, "the handshake says whose authority a call is made under");
 
   const listed = byId.get(2)!.result.tools;
-  assert.deepEqual(listed.map((x: { name: string }) => x.name), ["mesh-controller.push", "mesh-controller.status", "shop.price"],
+  assert.deepEqual(listed.map((x: { name: string }) => x.name),
+    ["mesh-controller.push", "mesh-controller.status", "node-dns-resolver.lookup", "shop.price"],
     "the modules' tools and the roles', named the way a person names them");
-  const price = listed[2];
+  // A node-scoped seat's verb takes the machine, and requires it (ADR 0169).
+  const lookup = listed[2];
+  assert.equal(lookup.inputSchema.properties.node.type, "string");
+  assert.deepEqual(lookup.inputSchema.required, ["node"]);
+  const price = listed[3];
   assert.ok(price.inputSchema, "a tool with no schema is one an agent cannot call");
   // A module's bare property map arrives as a schema an agent can read, its words kept — and
   // `node`, the machine to ask when the module runs on several (novox/hq ADR 0159), beside them.
@@ -169,3 +179,18 @@ test("a host calls the mesh's own verb through the seat", async (t) => {
   assert.ok(!result.isError, JSON.stringify(replies[0]));
   assert.deepEqual(JSON.parse(result.content[0].text), { output: "all quiet", ok: true });
 });
+
+test("a node-scoped seat's verb is asked of the machine named, and refused without one", async (t) => {
+  if (!url) return t.skip("MESH_TEST_NATS unset");
+  const credential = await aMeshAndACredential(t);
+  const replies = await driving(credential, [
+    { jsonrpc: "2.0", id: 1, method: "initialize", params: {} },
+    { jsonrpc: "2.0", id: 2, method: "tools/call", params: { name: "node-dns-resolver.lookup", arguments: { node: "anchor" } } },
+    { jsonrpc: "2.0", id: 3, method: "tools/call", params: { name: "node-dns-resolver.lookup", arguments: {} } },
+  ]);
+  const byId = new Map(replies.map((r) => [r.id, r]));
+  const answered = byId.get(2)!.result;
+  assert.ok(!answered.isError, JSON.stringify(answered));
+  assert.match(answered.content[0].text, /"machine": "anchor"/, "the machine's holder answered");
+  assert.match(byId.get(3)!.error?.message ?? JSON.stringify(byId.get(3)), /name the machine/);
+});