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Switchback MCP

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Switchback MCP

Switchback 用の MCP サーバー — AI エージェントのターンを複雑さで分類し、処理できる最も安価なモデルを選択します。Claude Desktop、Cursor、Cline、および任意の MCP クライアントにそのまま組み込めます。

npm Powers VibeKit

VibeKit によって構築 — 当社のホステッド製品のすべての「Auto」ターンを支える同じカスケードルーターです。詳細はこちら →

機能

Model Context Protocol 上で2つのツールを公開します:

  • classify_turn — ユーザーメッセージを受け取り、{tier: 0|1|2, why, fallback, durationMs} を返します。次のエージェントステップでフラッグシップモデルにコストをかけるか、安価なモデルに留まるかを判断するときに使用します。

  • recommend_model — ユーザーメッセージとモデルのラダー（安価 → フラッグシップ）を受け取り、そのラダーの中で処理できそうな最も安価なモデルを返します。classify_turn の便利なラッパーです。

両方のツールは OpenRouter 経由で単一の小規模モデル呼び出しを行います（デフォルト: openai/gpt-5.4-mini、約 $0.0001/回）。フェイルソフト: エラーが発生した場合は、エージェントをブロックせずに fallback: true 付きの tier 1 を返します。

Related MCP server: oracle-models

インストール

npm install -g vibekit-switchback-mcp

設定

OpenRouter キーを設定してください（https://openrouter.ai/keys で取得できます）:

export OPENROUTER_API_KEY=sk-or-...

オプション: 分類モデルを上書きする:

export SWITCHBACK_CLASSIFIER_MODEL=anthropic/claude-haiku-4.5

Claude Desktop

~/Library/Application Support/Claude/claude_desktop_config.json に追加してください:

{
  "mcpServers": {
    "switchback": {
      "command": "npx",
      "args": ["-y", "vibekit-switchback-mcp"],
      "env": {
        "OPENROUTER_API_KEY": "sk-or-..."
      }
    }
  }
}

Cursor / Cline / その他

stdio サーバーをサポートする任意の MCP クライアント。同じ npx 呼び出しを使用します。

呼び出し例

classify_turn:

{
  "userMessage": "rebuild the auth flow with passkeys"
}

返り値:

{
  "tier": 2,
  "why": "architectural rework + new auth method",
  "fallback": false,
  "durationMs": 412
}

recommend_model:

{
  "userMessage": "fix typo in README",
  "ladder": [
    "openai/gpt-5.4-mini",
    "openai/gpt-5.4",
    "openai/gpt-5.5"
  ]
}

返り値:

{
  "recommended_model": "openai/gpt-5.4-mini",
  "tier": 0,
  "ladder_size": 3,
  "classifier": { "tier": 0, "why": "trivial copy edit", "fallback": false, "durationMs": 318 }
}

使用すべき場面

  • マルチステップエージェント — ラウンド間でモデルを切り替えられる場合。

  • BYOK スタイルの製品 — すべてのルーティングをユーザーが選択したブランド内に留めたい場合。ユーザーごとにブランド固定のラダーを渡します。

  • コスト重視のオーケストレーター — 些細なターンにフラッグシップ料金を費やさないようにしたい場合。

使用すべきでない場面

  • ワンショットチャット補完 — 最初の呼び出し後にモデルを変更できない場合。代わりに OpenRouter の auto または NotDiamond/Martian を使用してください。

  • レイテンシが重要な 200ms 未満のファーストトークン UX — 分類器は 200〜500ms 追加します。

ライセンス

MIT。 LICENSE を参照してください。

VibeKit によって構築されました。コアライブラリは vibekit-switchback です — このパッケージは MCP ラッパーです。

Available Tools

2 tools
classify_turnA

Classify how complex a user request is on a 0/1/2 scale. Use this when you're orchestrating an agent and want to decide whether to spend on a flagship model (tier 2), a mid-tier model (tier 1), or stay cheap (tier 0). Returns {tier, why, fallback, durationMs}.

NameRequiredDescriptionDefault
userMessageYesThe user's request to classify. Capped at 1500 chars internally.
recentHistoryNoOptional. Last 1-2 assistant turns for context. Each capped at 200 chars internally.

TDQS

A3.7/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden. It does disclose the return shape ({tier, why, fallback, durationMs}) and explains the tier meanings, which adds value. However, it does not disclose potential side effects, fallback semantics, or internal behavior such as truncation limits beyond what the schema already contains.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences, front-loaded with the core action and scale, then followed by the use case and return shape. Every sentence earns its place with no wasted words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The schema is simple and the description covers purpose, use case, and return fields, but it does not explain the meanings of 'fallback' and 'durationMs', nor does it contrast with the sibling 'recommend_model'. This leaves gaps an agent might need to resolve before confidently choosing this tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description does not add parameter-specific detail beyond the schema; it only explains the tier scale, not how userMessage or recentHistory should be formatted beyond what the schema already states.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

Description states a specific verb ('Classify'), a resource ('user request'), and the 0/1/2 scale, making the tool's purpose immediately clear. It also ties the scale to model-tier decisions, but it does not explicitly differentiate from the sibling tool 'recommend_model'.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly says when to use it ('when you're orchestrating an agent and want to decide whether to spend...'), giving clear context for deployment. However, it does not state when not to use it or mention the alternative tool, so it lacks exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

recommend_modelA

Given a ladder of models (cheap → flagship) and a user message, return the cheapest model on the ladder that can plausibly handle it, plus reasoning. The ladder should be brand-locked (all-Anthropic, all-OpenAI, etc.) to honor your user's BYOK provider.

NameRequiredDescriptionDefault
ladderYesOrdered model ids, index 0 = cheapest. Example: ['openai/gpt-5.4-mini', 'openai/gpt-5.4', 'openai/gpt-5.5']
userMessageYesThe user's request.
recentHistoryNoOptional context. Last 1-2 assistant turns.

TDQS

A4/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the burden of explaining behavior. It states the tool returns a recommendation plus reasoning and enforces a brand-locked ladder, but it does not disclose what happens when no model is suitable, how 'plausibly' is determined, or whether the tool actually invokes any external model.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, no filler. The primary behavior is front-loaded in the first sentence, and the BYOK constraint earns its place in the second sentence.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description appropriately explains the expected return: cheapest model plus reasoning. It could be more explicit about edge cases, such as an incapable ladder or how 'recentHistory' should influence the selection, but the core invocation context is covered.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description adds useful context about ladder ordering and brand-locking, but it does not materially expand on the meaning of 'userMessage' or 'recentHistory' beyond what the schema already provides.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb ('return') and resource ('the cheapest model on the ladder') and clearly defines the task: select the cheapest plausible model for a user message and provide reasoning. It is easy to distinguish from the sibling 'classify_turn' because the purpose centers on model selection, not classification.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives clear context for when to use the tool: when a model ladder and a user message are available, and when BYOK provider constraints apply. It does not explicitly contrast with 'classify_turn' or state when not to use it, but the usage context is unambiguous enough.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 2 tool updatesv0.1.1
    • First observedclassify_turn
    • First observedrecommend_model
Deploy Server
Context Every Agent Can ShareAgents share what they learn, hand off work, and keep it when you switch models. Start with 5 GB free.fulcradynamics.comAd

TDQS

A3.8/5.0

Scored across 2 tools

Disambiguation3/5

The two tools both relate to routing user requests to models, so an agent could confuse classifying a turn with recommending a model. However, the inputs and outputs are distinct enough—one returns a tier, the other returns a specific model—to be workable with clear descriptions.

Naming Consistency5/5

Both tools follow a consistent verb_noun snake_case pattern: classify_turn and recommend_model. Naming is predictable and clearly indicates the action and object.

Tool Count3/5

With only two tools, the server feels thin, but the scope is narrow enough that both tools can earn their place. The count is borderline rather than egregiously insufficient.

Completeness4/5

The server covers the core routing workflow: classifying complexity and selecting a cost-appropriate model. Minor gaps exist, such as no combined route tool or ladder management, but agents can work around these using the provided inputs.

Maintenance

ActivityMaintained
ResponsivenessNo issues

Resources

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