mcp-router

name	mcp-router
description	MCP 服务器自动按需加载技能。避免常驻 MCP 导致的 token 浪费。 每次对话开始时检测任务类型，只加载当前任务必需的 MCP 服务器。 复用 github.com/JuliusBrussee/caveman (shrink proxy) 和 github.com/rtk-ai/rtk (output filter) 策略。
tags	["mcp","token-optimization","performance"]

MCP Router

Why

11 个 MCP 服务器常驻 = 每轮注入 ~11,000 tokens 的工具描述。按需求载可省 ~80% 的 MCP 注入开销。

Task → MCP Mapping

Task Type	What you do	Load These MCPs	Est. tokens/turn
coding	Write/edit code, review PRs	token-savior, entroly, github	~3,500
research	Search papers, academic work	token-savior, entroly, semantic-scholar	~3,000
ui	Design review, generate images/diagrams	token-savior, entroly, ui-expert-mcp, image-generation, diagram-generator	~5,500
debug	Deep debugging, complex reasoning	token-savior, entroly, thinking	~3,000
docs	Write docs, web fetch	token-savior, entroly	~2,000
ops	Deploy, server ops	token-savior, entroly	~2,000
full	Need everything	All 11 (use .mcp.json.full)	~11,000

Built-in alternatives — Prefer these over MCP servers to save tokens:

• File ops → Kimi Shell/Glob/ReadFile (no MCP overhead)
• Web fetch → Kimi WebFetch (no MCP overhead)
• Browser → Only use puppeteer when screenshots needed

How to Use

1. Auto-detect on session start

At the start of every conversation, read .mcp.json and compare against the user's first request. If the loaded MCPs don't match the task type:

1. State: "Current MCP set: [X, Y]. Task type: [coding]. Recommended: [X, Y, Z]."
2. Ask: "Switch to [coding] profile?" (or auto-switch if user previously approved)
3. Modify .mcp.json → reload

2. Switch command

When user says any of these, trigger a profile switch:

User says	Action
"查论文" / "search paper" / "semantic scholar"	Load semantic-scholar, unload others
"生成图片" / "image" / "diagram"	Load ui-expert-mcp + image-generation + diagram-generator
"调试" / "debug" / "think step by step"	Load thinking
"操作 GitHub" / "PR" / "issue"	Load github
"用全部 MCP" / "full mode"	Restore .mcp.json.full
"精简 MCP" / "minimal"	Keep only token-savior + entroly

3. One-off usage (no profile switch)

If user only needs an MCP for a single query:

1. Load it temporarily
2. Execute the tool call
3. Unload it immediately

This avoids paying the token cost for the rest of the conversation.

Configuration Files

File	Purpose
.mcp.json	Active config (2-3 MCPs max)
.mcp.json.full	Full config (all 11 MCPs)
.mcp.json.ondemand	Per-server snippets for manual copy
mcp-servers/mcp-shrink.js	Shrink proxy (compresses tool descriptions, ~30% savings)
scripts/rtk-filter.ps1	RTK-style shell output filter (reduces tool output tokens)

Token Budget Rules

• Input > 60K in one session → Start new session
• Tool output > 5K chars → Truncate or use rtk-filter.ps1
• Session switching → /compact before new task
• Never keep > 5 MCPs loaded simultaneously

Shrink Proxy

All MCP servers in .mcp.json and .mcp.json.ondemand are wrapped with mcp-servers/mcp-shrink.js. This intercepts tools/list responses and compresses description fields using caveman rules:

• Removes filler: "This tool allows you to..." → ""
• Removes hedging: "likely", "probably", "generally" → ""
• Removes articles: "a", "an", "the" → ""
• Preserves code, URLs, paths, identifiers

Saves ~30% on MCP description tokens with zero semantic loss.

RTK Output Filter

For shell commands that produce long output, use scripts/rtk-filter.ps1:

# Instead of: git status (2,000 tokens)
# Use:
.\scripts\rtk-filter.ps1 git status    # ~200 tokens

# Instead of: npm test (25,000 tokens on failure)
# Use:
.\scripts\rtk-filter.ps1 npm test      # ~2,500 tokens

# Supports: git, npm, cargo, pytest, docker, kubectl, ls, cat, grep

Or manually apply RTK principles to any shell output:

1. Filter: Strip progress bars, ASCII art, timestamps
2. Group: Aggregate by file/type instead of listing every line
3. Truncate: Select-Object -First 50, add "... (N more)"
4. Deduplicate: Collapse repeated lines with count

Verification

After any MCP profile switch, verify shrink proxy works:

1. Check .mcp.json uses "command": "node", "args": ["mcp-servers/mcp-shrink.js", ...]
2. Run a tool call → descriptions should be terse
3. If shrink fails, fall back to direct command (remove shrink wrapper)

Anti-patterns

❌ All 11 MCPs loaded for a simple code edit
❌ Loading MCPs preemptively "just in case"
❌ Forgetting to unload after one-off usage
❌ Using filesystem MCP when Kimi Shell/ReadFile works
❌ Using fetch MCP when Kimi WebFetch works
❌ Running npm test without rtk-filter.ps1 on large test suites