src/mcplocal/src/proxymodel/plugins/favourite-index.ts

@@ -26,12 +26,21 @@ import type { ToolDefinition } from '../types.js';
 /** Per-session state key holding the presented-name → canonical-name map. */
 const RESOLVER_KEY = 'favourite-index:resolver';
 
-/** The load-bearing "prefer favourite/" instruction (see module doc). */
+/**
+ * The load-bearing "prefer favourite" instruction (see module doc).
+ *
+ * Phrased in the WIRE form (underscore-joined): the HTTP boundary's
+ * WireNameCodec rewrites the presented `favourite/<tool>` and
+ * `all/<server>/<tool>` names to `favourite_<tool>` / `all_<server>_<tool>`
+ * before any client sees them, so prose naming the slash form would tell the
+ * model to call names that are not in its function list.
+ */
 export const FAVOURITE_INDEX_INSTRUCTION =
-  'Tools are indexed in two namespaces. PREFER favourite/<tool> — a short ' +
+  'Tools are indexed in two namespaces. PREFER the favourite_-prefixed tools ' +
-  'curated list of the common tools that covers most tasks; reach for these ' +
+  '— a short curated list of the common tools that covers most tasks; reach ' +
-  'first. Use the full catalog under all/<server>/<tool> only if nothing in ' +
+  'for these first. Use the full catalog under the all_-prefixed names only ' +
-  "favourites fits. (read_prompts gives this project's own guidance.)";
+  "if nothing in favourites fits. (read_prompts gives this project's own " +
+  'guidance.)';
 
 export interface FavouriteIndexConfig {
   /** Canonical `server/tool` names to surface as favourites, in display order. */

src/mcplocal/src/proxymodel/plugins/gate.ts

@@ -16,6 +16,7 @@ import type { TagMatchResult } from '../../gate/tag-matcher.js';
 import { LlmPromptSelector, pickCompletionText, type ServerInfer } from '../../gate/llm-selector.js';
 import type { ProviderRegistry } from '../../providers/registry.js';
 import { withTimeout, TimeoutError } from '../../util/with-timeout.js';
+import { sanitizeWireName } from '../../util/wire-names.js';
 
 /** Cap on the gate's LLM prompt-selection. A slow/thinking LLM must never block
  * begin_session — on timeout we fall back to deterministic tag matching. */
@@ -115,13 +116,15 @@ export function createGatePlugin(config: GatePluginConfig = {}): ProxyModelPlugi
       );
       parts.push(`\n${gateInstructions}`);
 
-      // Append tool inventory (names only)
+      // Append tool inventory (names only). Sanitized to the wire charset:
+      // the boundary WireNameCodec serves `server_tool`, so prose listing the
+      // canonical `server/tool` would name functions the model cannot call.
       try {
         const tools = await ctx.discoverTools();
         if (tools.length > 0) {
           parts.push('\nAvailable MCP server tools (accessible after begin_session):');
           for (const t of tools) {
-            parts.push(`  ${t.name}`);
+            parts.push(`  ${sanitizeWireName(t.name)}`);
           }
         }
       } catch {
@@ -424,13 +427,14 @@ async function handleBeginSession(
   );
   responseParts.push(encouragement);
 
-  // Append tool inventory (names only)
+  // Append tool inventory (names only) — wire charset, see the initialize
+  // inventory note.
   try {
     const tools = await ctx.discoverTools();
     if (tools.length > 0) {
       responseParts.push('\nAvailable MCP server tools:');
       for (const t of tools) {
-        responseParts.push(`  ${t.name}`);
+        responseParts.push(`  ${sanitizeWireName(t.name)}`);
       }
     }
   } catch {

src/mcplocal/tests/router-gate.test.ts

@@ -525,8 +525,11 @@ describe('McpRouter gating', () => {
       );
 
       const result = res.result as { instructions: string };
-      expect(result.instructions).toContain('ha/get_entities');
+      // Wire form: prose must name what the client can actually call — the
-      expect(result.instructions).toContain('node-red/get_flows');
+      // boundary WireNameCodec serves underscore-joined names.
+      expect(result.instructions).toContain('ha_get_entities');
+      expect(result.instructions).toContain('node-red_get_flows');
+      expect(result.instructions).not.toContain('ha/get_entities');
       expect(result.instructions).toContain('after begin_session');
       // Descriptions should NOT be in init instructions (names only)
       expect(result.instructions).not.toContain('Get all entities');
@@ -544,7 +547,9 @@ describe('McpRouter gating', () => {
       );
 
       const text = (res.result as { content: Array<{ text: string }> }).content[0]!.text;
-      expect(text).toContain('ha/get_entities');
+      // Wire form in the inventory (see the initialize-instructions test).
+      expect(text).toContain('ha_get_entities');
+      expect(text).not.toContain('ha/get_entities');
       expect(text).not.toContain('Get all entities');
     });