MCP RAG Server

Instructions

Implementation Reference

• src/mcp/tools.ts:81-97 (handler)

  Handler for 'get_chunk' tool that retrieves a document chunk by ID. Calls ragService.getChunk(args.id), returns the chunk with success status, or error if not found. Formats response with chunk id, content, metadata, and uri.

  case 'get_chunk':
    const chunk = await ragService.getChunk(args.id);
    if (!chunk) {
      return {
        success: false,
        error: 'Chunk not found'
      };
    }
    return {
      success: true,
      chunk: {
        id: chunk.id,
        content: chunk.content,
        metadata: chunk.metadata,
        uri: `rag://doc/${chunk.metadata.source}#${chunk.id}`
      }
    };

• src/services/vectorStore.ts:157-180 (handler)

  Core implementation of getChunk that retrieves a chunk by ID. Attempts ChromaDB query first, falls back to in-memory Map storage if ChromaDB fails. Returns DocumentChunk object or null if not found.

  async getChunk(id: string): Promise<DocumentChunk | null> {
    if (this.collection) {
      try {
        const results = await this.collection.get({
          ids: [id]
        });
  
        if (!results.documents || results.documents.length === 0) {
          return null;
        }
  
        return {
          id: results.ids[0],
          content: results.documents[0],
          metadata: results.metadatas[0]
        };
      } catch (error) {
        console.warn('ChromaDB getChunk failed, falling back to memory:', error);
        return this.chunks.get(id) || null;
      }
    } else {
      return this.chunks.get(id) || null;
    }
  }

• src/mcp/tools.ts:33-46 (registration)

  Tool registration defining 'get_chunk' with description 'Retrieve a specific document chunk by its ID'. Input schema requires an 'id' string parameter identifying the chunk to retrieve.

  {
    name: 'get_chunk',
    description: 'Retrieve a specific document chunk by its ID',
    inputSchema: {
      type: 'object',
      properties: {
        id: {
          type: 'string',
          description: 'The unique identifier of the chunk to retrieve'
        }
      },
      required: ['id']
    }
  },

• src/services/ragService.ts:66-68 (helper)

  RAGService wrapper method that delegates getChunk calls to the underlying VectorStore instance.

  async getChunk(id: string): Promise<DocumentChunk | null> {
    return await this.vectorStore.getChunk(id);
  }

• src/services/vectorStore.ts:5-16 (schema)

  DocumentChunk interface defining the structure of document chunks with id, content, and metadata fields including source, chunkIndex, totalChunks, title, page, and distance.

  export interface DocumentChunk {
    id: string;
    content: string;
    metadata: {
      source: string;
      chunkIndex: number;
      totalChunks: number;
      title?: string;
      page?: number;
      distance?: number;
    };
  }