Langfuse MCP Server

Instructions

Implementation Reference

• src/tools/get-dataset-item.ts:10-26 (handler)

  The primary handler function for the 'get_dataset_item' tool. It takes a Langfuse client and arguments, fetches the dataset item by ID, and returns formatted content or error.

  export async function getDatasetItem(
    client: LangfuseAnalyticsClient,
    args: GetDatasetItemArgs
  ) {
    try {
      const data = await client.getDatasetItem(args.itemId);
      return {
        content: [{ type: 'text' as const, text: JSON.stringify(data, null, 2) }],
      };
    } catch (error) {
      const errorMessage = error instanceof Error ? error.message : String(error);
      return {
        content: [{ type: 'text' as const, text: `Error: ${errorMessage}` }],
        isError: true,
      };
    }
  }

• src/tools/get-dataset-item.ts:4-6 (schema)

  Zod schema for validating input arguments to the get_dataset_item tool, requiring a non-empty itemId string.

  export const getDatasetItemSchema = z.object({
    itemId: z.string().min(1).describe('ID of the dataset item to retrieve'),
  });

• src/index.ts:1118-1121 (registration)

  Switch case in the CallToolRequestSchema handler that parses arguments using the schema and dispatches to the getDatasetItem handler function.

  case 'get_dataset_item': {
    const args = getDatasetItemSchema.parse(request.params.arguments);
    return await getDatasetItem(this.client, args);
  }

• src/index.ts:744-757 (registration)

  Tool registration entry in the listTools handler, defining name, description, and input schema for get_dataset_item.

  {
    name: 'get_dataset_item',
    description: 'Get detailed information about a specific dataset item.',
    inputSchema: {
      type: 'object',
      properties: {
        itemId: {
          type: 'string',
          description: 'ID of the dataset item to retrieve',
        },
      },
      required: ['itemId'],
    },
  },

• src/langfuse-client.ts:517-533 (helper)

  LangfuseAnalyticsClient method that makes the actual API call to retrieve a dataset item by ID, used by the tool handler.

  async getDatasetItem(itemId: string): Promise<any> {
    const authHeader = 'Basic ' + Buffer.from(
      `${this.config.publicKey}:${this.config.secretKey}`
    ).toString('base64');
  
    const response = await fetch(`${this.config.baseUrl}/api/public/dataset-items/${encodeURIComponent(itemId)}`, {
      headers: {
        'Authorization': authHeader,
      },
    });
  
    if (!response.ok) {
      await this.handleApiError(response, 'Get Dataset Item');
    }
  
    return await response.json();
  }