fix(coding-agent): make prompt snippets opt in closes #2285

packages/coding-agent/src/core/extensions/types.ts

@@ -339,7 +339,7 @@ export interface ToolDefinition<TParams extends TSchema = TSchema, TDetails = un
 	label: string;
 	/** Description for LLM */
 	description: string;
-	/** Optional one-line snippet for the Available tools section in the default system prompt. Falls back to description when omitted. */
+	/** Optional one-line snippet for the Available tools section in the default system prompt. Custom tools are omitted from that section when this is not provided. */
 	promptSnippet?: string;
 	/** Optional guideline bullets appended to the default system prompt Guidelines section when this tool is active. */
 	promptGuidelines?: string[];

packages/coding-agent/src/core/system-prompt.ts

@@ -94,9 +94,10 @@ export function buildSystemPrompt(options: BuildSystemPromptOptions = {}): strin
 	// Build tools list based on selected tools.
 	// Built-ins use toolDescriptions. Custom tools can provide one-line snippets.
 	const tools = selectedTools || ["read", "bash", "edit", "write"];
+	const visibleTools = tools.filter((name) => name in toolDescriptions || toolSnippets?.[name]);
 	const toolsList =
-		tools.length > 0
-			? tools
+		visibleTools.length > 0
+			? visibleTools
 					.map((name) => {
 						const snippet = toolSnippets?.[name] ?? toolDescriptions[name] ?? name;
 						return `- ${name}: ${snippet}`;