`mcp-sage`

An MCP (Model Context Protocol) server that provides tools for sending prompts to OpenAI's GPT-5, GPT-4.1, Google's Gemini 2.5 Pro, or Anthropic's Claude Opus 4.1 based on token count and configuration. The tools embed all referenced filepaths (recursively for folders) in the prompt. This is useful for getting second opinions or detailed code reviews from models that can handle large amounts of context accurately.

Rationale

I make heavy use of Claude Code. It's a great product that works well for my workflow. Newer models with large amounts of context seem really useful though for dealing with more complex codebases where more context is needed. This lets me continue to use Claude Code as a development tool while leveraging the large context capabilities of GPT-5, Gemini 2.5 Pro, and other models to augment Claude Code's limited context.

Model Selection

The server automatically selects the appropriate model based on token count, with configuration defined in models.yaml:

For smaller contexts (≤ 400K tokens): Uses OpenAI's GPT-5 (if OPENAI_API_KEY is set)
For medium contexts (≤ 1M tokens): Uses Google's Gemini 2.5 Pro (if GEMINI_API_KEY is set)
For fallback (≤ 1M tokens): Uses OpenAI's GPT-4.1
If the content exceeds 1M tokens: Returns an informative error

Fallback behavior:

API Key Fallback:
- If OPENAI_API_KEY is missing, Gemini will be used for all contexts within its 1M token limit
- If GEMINI_API_KEY is missing, only smaller contexts can be processed with OpenAI models
- If required API keys are missing, an informative error is returned

Inspiration

This project draws inspiration from two other open source projects:

simonw/files-to-prompt for the file compression
asadm/vibemode for the idea and prompt to send the entire repo to Gemini for wholesale edit suggestions
PhialsBasement/Chain-of-Recursive-Thoughts inspiration for the debate functionality

Overview

This project implements an MCP server that exposes two primary tools:

`sage-opinion`

Takes a prompt and a list of file/dir paths as input
Packs the files into a structured XML format
Measures the token count and selects the appropriate model:
- GPT-5 for ≤ 400K tokens
- Gemini 2.5 Pro for > 400K and ≤ 1M tokens
- GPT-4.1 as fallback for ≤ 1M tokens
Sends the combined prompt + context to the selected model
Returns the model's response

`sage-review`

Takes an instruction for code changes and a list of file/dir paths as input
Packs the files into a structured XML format
Measures the token count and selects the appropriate model:
- GPT-5 for ≤ 400K tokens
- Gemini 2.5 Pro for > 400K and ≤ 1M tokens
- GPT-4.1 as fallback for ≤ 1M tokens
Creates a specialized prompt instructing the model to format responses using SEARCH/REPLACE blocks
Sends the combined context + instruction to the selected model
Returns edit suggestions formatted as SEARCH/REPLACE blocks for easy implementation

Debate Mode

Both sage-opinion and sage-review support an optional debate mode that can be enabled by adding debate: true to the arguments. When enabled, the system orchestrates a structured debate between multiple models to generate higher-quality responses.

1. Multi-Model Debate Flow

flowchart TD
  S0[Start Debate] -->|determine models, judge, budgets| R1

  subgraph R1["Round 1"]
    direction TB
    R1GEN["Generation Phase<br/>*ALL models run in parallel*"]
    R1GEN --> R1CRIT["Critique Phase<br/>*ALL models critique others in parallel*"]
  end

  subgraph RN["Rounds 2 to N"]
    direction TB
    SYNTH["Synthesis Phase<br/>*every model refines own plan*"]
    SYNTH --> CONS[Consensus Check]
    CONS -->|Consensus reached| JUDGE
    CONS -->|No consensus & round < N| CRIT["Critique Phase<br/>*models critique in parallel*"]
    CRIT --> SYNTH
  end

  R1 --> RN
  JUDGE[Judgment Phase<br/>*judge model selects/merges response*]
  JUDGE --> FP[Final Response]

  classDef round fill:#e2eafe,stroke:#4169E1;
  class R1GEN,R1CRIT,SYNTH,CRIT round;
  style FP fill:#D0F0D7,stroke:#2F855A,stroke-width:2px
  style JUDGE fill:#E8E8FF,stroke:#555,stroke-width:1px

Key phases in the multi-model debate:

Setup Phase

The system determines available models, selects a judge, and allocates token budgets

Round 1

Generation Phase - Every available model (A, B, C, etc.) generates its response in parallel
Critique Phase - Each model reviews all other responses (never its own) and produces structured critiques in parallel

Rounds 2 to N (N defaults to 3)

Synthesis Phase - Each model improves its previous response using critiques it received (models work in parallel)
Consensus Check - The judge model scores similarity between all current responses
- If score ≥ 0.9, the debate stops early and jumps to Judgment
Critique Phase - If consensus is not reached AND we're not in the final round, each model critiques all other responses again (in parallel)

Judgment Phase

After completing all rounds (or reaching early consensus), the judge model (Claude Opus 4.1 by default):
- For sage-opinion: Selects the single best response (no synthesis)
- For sage-review: Can either select the best response OR merge multiple responses
- Provides a confidence score for its selection/synthesis

2. Self-Debate Flow - Single Model Available

flowchart TD
  SD0[Start Self-Debate] --> R1

  subgraph R1["Round 1 - Initial Responses"]
    direction TB
    P1[Generate Response 1] --> P2[Generate Response 2<br/>*different approach*]
    P2 --> P3[Generate Response 3<br/>*different approach*]
  end

  subgraph RN["Rounds 2 to N"]
    direction TB
    REF[Generate Improved Response<br/>*addresses weaknesses in all previous responses*]
    DEC{More rounds left?}
    REF --> DEC
    DEC -->|Yes| REF
  end

  R1 --> RN
  DEC -->|No| FP[Final Response = last response generated]

  style FP fill:#D0F0D7,stroke:#2F855A,stroke-width:2px

When only one model is available, a Chain of Recursive Thoughts (CoRT) approach is used:

Initial Burst - The model generates three distinct responses, each taking a different approach
Refinement Rounds - For each subsequent round (2 to N, default N=3):
- The model reviews all previous responses
- It critiques them internally, identifying strengths and weaknesses
- It produces one new improved response that addresses limitations in earlier responses
Final Selection - The last response generated becomes the final output

What Actually Happens in Code (quick reference)

Phase / Functionality	Code Location	Notes
Generation Prompts	prompts/debatePrompts.generatePrompt	Creates initial responses from each model
Critique Prompts	prompts/debatePrompts.critiquePrompt	Uses "## Critique of {ID}" sections
Synthesis Prompts	prompts/debatePrompts.synthesizePrompt	Model revises its own response
Consensus Check	orchestrator/debateOrchestrator	Judge model returns JSON with `consensusScore`
Judgment	prompts/debatePrompts.judgePrompt	Judge returns final response + confidence
Self-Debate Prompt	prompts/debatePrompts.selfDebatePrompt	Chain-of-Recursive-Thoughts loop

Performance and Cost Considerations

⚠️ Important: When using debate mode:

It can take more time to complete (2-5 minutes with multiple models)
Consumes more API tokens due to multiple rounds of debate
Incurs higher costs than single-model approaches

Typical resource usage:

Multi-model debate: 2-4x more tokens than a single model approach
Processing time: 2-5 minutes depending on complexity and model availability
API costs vary by models used and complexity

Prerequisites

Node.js (v18 or later)
API keys for the models you want to use:
- OpenAI API key (for GPT-5 and GPT-4.1)
- Google Gemini API key (for Gemini 2.5 Pro)
- Anthropic API key (for Claude Opus 4.1 as judge in debates)

Note: While the server can function with just one API key, it works best when all three are provided. This enables:

Optimal model selection based on token count
Multi-model debates for higher quality responses
Claude Opus 4.1 as an impartial judge in debate mode

Installation

Installing via Smithery

To install Sage for Claude Desktop automatically via Smithery:

npx -y @smithery/cli install @jalehman/mcp-sage --client claude

Installing manually

# Clone the repository
git clone https://github.com/your-username/mcp-sage.git
cd mcp-sage

# Install dependencies
npm install

# Build the project
npm run build

Environment Variables

Set the following environment variables:

OPENAI_API_KEY: Your OpenAI API key (for GPT-5 and GPT-4.1 models)
GEMINI_API_KEY: Your Google Gemini API key (for Gemini 2.5 Pro)
ANTHROPIC_API_KEY: Your Anthropic API key (for Claude Opus 4.1)

Recommended: Provide all three API keys for the best experience. This ensures:

The server can select the optimal model for any token count
Debate mode works with multiple diverse models
Claude Opus 4.1 serves as an effective judge in debates

Usage

After building with npm run build, add the following to your MCP configuration:

OPENAI_API_KEY=your_openai_key GEMINI_API_KEY=your_gemini_key node /path/to/this/repo/dist/index.js

You can also use environment variables set elsewhere, like in your shell profile.

Prompting

To get a second opinion on something just ask for a second opinion.

To get a code review, ask for a code review or expert review.

Both of these benefit from providing paths of files that you wnat to be included in context, but if omitted the host LLM will probably infer what to include.

Debugging and Monitoring

The server provides detailed monitoring information via the MCP logging capability. These logs include:

Token usage statistics and model selection
Number of files and documents included in the request
Request processing time metrics
Error information when token limits are exceeded

Logs are sent via the MCP protocol's notifications/message method, ensuring they don't interfere with the JSON-RPC communication. MCP clients with logging support will display these logs appropriately.

Example log entries:

Token usage: 1,234 tokens. Selected model: gpt-5-2025-08-07 (limit: 400,000 tokens)
Files included: 3, Document count: 3
Sending request to OpenAI gpt-5-2025-08-07 with 1,234 tokens...
Received response from gpt-5-2025-08-07 in 982ms

Token usage: 435,678 tokens. Selected model: gemini-2.5-pro (limit: 1,000,000 tokens)
Files included: 25, Document count: 18
Sending request to Gemini with 435,678 tokens...
Received response from gemini-2.5-pro in 3240ms

Using the Tools

sage-opinion Tool

The sage-opinion tool accepts the following parameters:

prompt (string, required): The prompt to send to the selected model
paths (array of strings, required): List of file paths to include as context
debate (boolean, optional): Enable multi-model debate mode for higher quality responses

Example MCP tool call (using JSON-RPC 2.0):

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "sage-opinion",
    "arguments": {
      "prompt": "Explain how this code works",
      "paths": ["path/to/file1.js", "path/to/file2.js"]
    }
  }
}

sage-review Tool

The sage-review tool accepts the following parameters:

instruction (string, required): The specific changes or improvements needed
paths (array of strings, required): List of file paths to include as context
debate (boolean, optional): Enable multi-model debate mode for higher quality responses

Example MCP tool call (using JSON-RPC 2.0):

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "sage-review",
    "arguments": {
      "instruction": "Add error handling to the function",
      "paths": ["path/to/file1.js", "path/to/file2.js"]
    }
  }
}

The response will contain SEARCH/REPLACE blocks that you can use to implement the suggested changes:

<<<<<<< SEARCH
function getData() {
  return fetch('/api/data')
    .then(res => res.json());
}
=======
function getData() {
  return fetch('/api/data')
    .then(res => {
      if (!res.ok) {
        throw new Error(`HTTP error! Status: ${res.status}`);
      }
      return res.json();
    })
    .catch(error => {
      console.error('Error fetching data:', error);
      throw error;
    });
}
>>>>>>> REPLACE

When using debate mode with either tool, the system will:

Generate initial responses from multiple models (GPT-5 and Gemini by default)
Have models critique each other's responses
Allow models to refine their responses based on critiques
Use a judge model (Claude Opus 4.1 by default) to select or synthesize the best response

This results in more thoughtful and comprehensive responses at the cost of additional time and API usage.

Running the Tests

To test the tools:

# Test the sage-opinion tool
OPENAI_API_KEY=your_openai_key GEMINI_API_KEY=your_gemini_key node test/run-test.js

# Test the sage-review tool
OPENAI_API_KEY=your_openai_key GEMINI_API_KEY=your_gemini_key node test/test-expert.js

# Test debate mode
OPENAI_API_KEY=your_openai_key GEMINI_API_KEY=your_gemini_key ANTHROPIC_API_KEY=your_anthropic_key node test/run-sage-opinion-debate.js

Note: Tests using debate mode may take 2-5 minutes to run as they orchestrate multi-model interactions.

Project Structure

src/index.ts: The main MCP server implementation with tool definitions
src/pack.ts: Tool for packing files into a structured XML format
src/tokenCounter.ts: Utilities for counting tokens in a prompt
src/gemini.ts: Gemini API client implementation
src/openai.ts: OpenAI API client implementation for O3 model
src/orchestrator/debateOrchestrator.ts: Multi-model debate orchestration
src/prompts/debatePrompts.ts: Templates for debate prompts and instructions
test/run-test.js: Test for the sage-opinion tool
test/test-expert.js: Test for the sage-review tool
test/run-sage-opinion-debate.js: Test for debate mode functionality

License

ISC