feat(tools): implement deferred tool discovery with tool_search

[Jonnytoshen]

Summary

Implements a deferred tool discovery mechanism so the agent only loads MCP tool schemas on demand, keeping the system prompt lean while still making all tools accessible via tool_search.

Changes

• ToolDefinition interface — added shouldDefer and searchHint metadata fields
• MCP registration — all MCP tools are now marked shouldDefer: true with auto-generated searchHint from their server name and description
• ToolRegistry — tracks which deferred tools have been discovered via a discoveredTools Set
• searchTools() — exact-name lookup for deferred tools; adds discovered tools to the active set
• getActiveTools() / getDeferredToolSummary() — control prompt visibility and generate the "available but deferred" hint injected into the system prompt
• countTokenEstimate() — debug/monitoring utility that estimates prompt token impact split between active and deferred tools
• ToolSearch tool — new built-in tool_search tool; the agent calls it to hydrate a deferred tool's full schema before invoking it
• CLI (src/index.ts) — wires the new APIs into the startup system prompt and tool dashboard table (shouldDefer column + token stats)

How It Works

Startup
  └── getDeferredToolSummary() → appended to SYSTEM prompt
        "以下工具可用，但需要先通过 tool_search 搜索获取完整定义: ..."

Agent needs an MCP tool
  └── calls tool_search("mcp__github__list_issues")
        └── searchTools() marks tool as discovered
              └── next turn: tool appears in toAISDKFormat() output
                    └── agent calls the real tool

Commits

#	Hash	Message
1	e0fe4b6	feat(tools): add deferred metadata fields to tool definition
2	c039f19	feat(tools): mark MCP tools as deferred with search hints
3	8d21962	feat(tools): add discovered tool tracking in registry
4	7d424a7	feat(tools): add exact-name lookup API for deferred tools
5	03f73bb	feat(tools): add active and deferred tool summary APIs
6	6fd8e6d	feat(tools): add token estimate stats for tool schemas
7	195866a	feat(tools): add tool_search for deferred tool schema loading
8	fe96037	feat(cli): wire dynamic tool discovery into startup prompt and tool dashboard

Files Changed

File	+/-
src/tools/tool-registry.ts	+107
src/tools/ToolSearch.ts	+35 (new)
src/index.ts	+19 / -9

Checklist

• Lint passes (pnpm lint)
• No breaking changes to existing tool registration API
• All MCP tools automatically deferred — no per-tool configuration needed
• Backward compatible: non-deferred tools behave identically to before

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