claude-code/packages/builtin-tools/src/tools/SearchExtraToolsTool/prompt.ts

import { getFeatureValue_CACHED_MAY_BE_STALE } from 'src/services/analytics/growthbook.js'
import type { Tool } from 'src/Tool.js'
import { CORE_TOOLS } from 'src/constants/tools.js'

export { SEARCH_EXTRA_TOOLS_TOOL_NAME } from './constants.js'

import { SEARCH_EXTRA_TOOLS_TOOL_NAME } from './constants.js'

const PROMPT_HEAD = `Search for deferred tools by name or keyword. LOW PRIORITY — only use this tool when no core tool can accomplish the task. Core tools (Read, Edit, Write, Bash, Glob, Grep, Agent, WebFetch, WebSearch, Skill) are always available and should be used directly. This tool is for discovering additional capabilities like MCP tools, cron scheduling, worktree management, agent teams (TeamCreate, TeamDelete, SendMessage), etc.

`

// Matches isDeferredToolsDeltaEnabled in searchExtraTools.ts (not imported —
// searchExtraTools.ts imports from this file). When enabled: tools announced
// via system-reminder attachments. When disabled: prepended
// <available-deferred-tools> block (pre-gate behavior).
function getToolLocationHint(): string {
  const deltaEnabled =
    process.env.USER_TYPE === 'ant' ||
    getFeatureValue_CACHED_MAY_BE_STALE('tengu_glacier_2xr', false)
  return deltaEnabled
    ? 'Deferred tools appear by name in <system-reminder> messages.'
    : 'Deferred tools appear by name in <available-deferred-tools> messages.'
}

const PROMPT_TAIL = ` Returns matching tool names.

IMPORTANT: ExecuteExtraTool is always available in your tool list. After this search returns tool names, you MUST call ExecuteExtraTool with {"tool_name": "<returned_name>", "params": {...}} to invoke the deferred tool. This is the ONLY way to execute deferred tools — do not read source code or analyze whether the tool is callable, just use ExecuteExtraTool directly.

Query forms:
- "select:CronCreate,Snip" — fetch these exact tools by name
- "discover:schedule cron job" — pure discovery, returns tool info (name, description) without loading. Use when you want to understand available tools before deciding which to invoke.
- "notebook jupyter" — keyword search, up to max_results best matches
- "+slack send" — require "slack" in the name, rank by remaining terms`

/**
 * Check if a tool should be deferred (requires SearchExtraTools to load).
 * A tool is deferred if it is NOT in CORE_TOOLS and does NOT have alwaysLoad: true.
 * Core tools are always loaded — never deferred.
 * All other tools (non-core built-in + all MCP tools) are deferred
 * and must be discovered via SearchExtraToolsTool / ExecuteExtraTool.
 */
export function isDeferredTool(tool: Tool): boolean {
  // Explicit opt-out via _meta['anthropic/alwaysLoad']
  if (tool.alwaysLoad === true) return false

  // Core tools are always loaded — never deferred
  if (CORE_TOOLS.has(tool.name)) return false

  // Everything else (non-core built-in + all MCP tools) is deferred
  return true
}

/**
 * Format one deferred-tool line for the <available-deferred-tools> user
 * message. Search hints (tool.searchHint) are not rendered — the
 * hints A/B (exp_xenhnnmn0smrx4, stopped Mar 21) showed no benefit.
 */
export function formatDeferredToolLine(tool: Tool): string {
  return tool.name
}

export function getPrompt(): string {
  return PROMPT_HEAD + getToolLocationHint() + PROMPT_TAIL
}