Langfuse MCP Server

Instructions

Implementation Reference

• src/tools/get-observation-detail.ts:10-37 (handler)

  Core handler function that fetches the observation detail using the Langfuse client and returns formatted content or error.

  export async function getObservationDetail(
    client: LangfuseAnalyticsClient,
    args: GetObservationDetailArgs
  ) {
    try {
      const observationData = await client.getObservation(args.observationId);
  
      return {
        content: [
          {
            type: 'text' as const,
            text: JSON.stringify(observationData, null, 2),
          },
        ],
      };
    } catch (error) {
      const errorMessage = error instanceof Error ? error.message : String(error);
      return {
        content: [
          {
            type: 'text' as const,
            text: `Error getting observation detail: ${errorMessage}`,
          },
        ],
        isError: true,
      };
    }
  }

• src/tools/get-observation-detail.ts:4-6 (schema)

  Zod schema for input validation of the get_observation_detail tool.

  export const getObservationDetailSchema = z.object({
    observationId: z.string().describe('The observation ID to retrieve detailed information for'),
  });

• src/index.ts:526-539 (registration)

  Tool definition in the allTools array used by listTools handler to expose the tool with its schema.

  {
    name: 'get_observation_detail',
    description: 'Get detailed information about a specific observation by ID.',
    inputSchema: {
      type: 'object',
      properties: {
        observationId: {
          type: 'string',
          description: 'The observation ID to retrieve detailed information for',
        },
      },
      required: ['observationId'],
    },
  },

• src/index.ts:1062-1065 (registration)

  Dispatch case in the central CallToolRequestSchema handler that parses arguments and invokes the tool handler.

  case 'get_observation_detail': {
    const args = getObservationDetailSchema.parse(request.params.arguments);
    return await getObservationDetail(this.client, args);
  }

• src/tools/get-observation-detail.ts:8-8 (schema)

  TypeScript type inferred from the Zod schema for type safety.

  export type GetObservationDetailArgs = z.infer<typeof getObservationDetailSchema>;