From 8b4bd595723a1cf58871d6653abb8fe1cdcd87ec Mon Sep 17 00:00:00 2001
From: Richard Zink <richard@familie-zink.org>
Date: Thu, 12 Nov 2026 12:12:19 +0100
Subject: [PATCH] mcp_search also points to built-in tools and their
 availability
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Models looked for generate_3d with mcp_search, which only searched MCP
servers, and concluded it did not exist (the chat had been in plan mode, then
switched to build). The search now lists matching built-in tools first:
"available – call it directly" or "not in the read-only mode plan – ask the
user to switch to build mode".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 CHANGELOG.md      |  9 +++++++++
 server/src/mcp.rs | 43 +++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0e7652f..b831cb3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,15 @@
 All notable changes to CodeCraft. Versions follow [Semantic Versioning](https://semver.org/);
 until 1.0, minor versions may contain breaking changes.
 
+## [Unreleased]
+
+### Fixed
+
+- **Models did not find built-in tools via `mcp_search`** (e.g. `generate_3d` in a chat that
+  had just been switched from plan to build): the search only looked at MCP servers. It now also
+  lists matching built-in tools and says whether the current mode has them ("available – call it
+  directly", or "not in the read-only mode plan – ask the user to switch to build").
+
 ## [v202611-00024] – 2026-11-12
 
 ### Added
diff --git a/server/src/mcp.rs b/server/src/mcp.rs
index 67b840e..28cffec 100644
--- a/server/src/mcp.rs
+++ b/server/src/mcp.rs
@@ -558,6 +558,42 @@ impl McpManager {
 /// Search the on-demand MCP tools by keywords.
 pub struct McpSearch;
 
+/// Built-in tools matching the search words, with their availability in the current mode.
+fn builtin_matches(ctx: &ToolCtx, words: &[&str]) -> String {
+    if words.is_empty() {
+        return String::new();
+    }
+    let app = &ctx.app;
+    let owner_id = app.session(&ctx.session_id).ok().and_then(|s| s.owner_id);
+    let owner_user = owner_id.as_deref().and_then(|id| app.store.user(id).ok().flatten());
+    let root = app.root_for(owner_id.as_deref(), &ctx.cwd);
+    let agent = crate::prompts::find_agent_for(app, &root, &ctx.cwd, &ctx.agent, owner_id.as_deref());
+    let available: std::collections::HashSet<String> = crate::runner::available_tools(app, &agent, owner_user.as_ref()).iter().map(|t| t.name().to_string()).collect();
+    let mut hits: Vec<(usize, String)> = crate::tools::builtin_tools()
+        .iter()
+        .map(|t| {
+            let name = t.name().to_lowercase();
+            let desc = t.description().to_lowercase();
+            let score: usize = words.iter().map(|w| if name.contains(w) { 3 } else if desc.contains(w) { 1 } else { 0 }).sum();
+            let state = if available.contains(t.name()) {
+                "available – call it directly".to_string()
+            } else if agent.read_only && !t.read_only() {
+                format!("exists, but not in the read-only mode \"{}\" – ask the user to switch to build mode", agent.name)
+            } else {
+                format!("exists, but not available in mode \"{}\" (or disabled in the settings)", agent.name)
+            };
+            (score, format!("- {}: {state}", t.name()))
+        })
+        .filter(|(s, _)| *s >= 2 || words.len() == 1 && *s >= 1)
+        .collect();
+    hits.sort_by(|a, b| b.0.cmp(&a.0));
+    if hits.is_empty() {
+        return String::new();
+    }
+    let list: Vec<String> = hits.into_iter().take(4).map(|(_, l)| l).collect();
+    format!("Built-in tools (not MCP – call them directly by name, not via mcp_call):\n{}\n\n", list.join("\n"))
+}
+
 #[async_trait]
 impl Tool for McpSearch {
     fn name(&self) -> &str {
@@ -602,10 +638,13 @@ impl Tool for McpSearch {
             .filter(|(s, _)| *s > 0 || words.is_empty())
             .collect();
         scored.sort_by(|a, b| b.0.cmp(&a.0));
+        // Models also look here for built-in tools (e.g. generate_3d): say that they exist,
+        // whether this mode has them, and that they are called directly.
+        let builtin = if server.is_none() { builtin_matches(ctx, &words) } else { String::new() };
         if scored.is_empty() {
-            return Ok(ToolOutput::text("No matching tools. Try other keywords or another server."));
+            return Ok(ToolOutput::text(if builtin.is_empty() { "No matching tools. Try other keywords or another server.".to_string() } else { builtin }));
         }
-        let mut out = String::new();
+        let mut out = builtin;
         for (_, t) in scored.iter().take(8) {
             let desc: String = t.info.description.chars().take(300).collect();
             out.push_str(&format!("## {}\n{}\nInput schema: {}\n\n", t.full_name, desc, t.info.input_schema));