MCP Glucose Server

Instructions

Implementation Reference

• src/api-client.ts:74-96 (handler)

  Core handler implementation in HealthDataAPI class. Fetches the latest glucose reading via HTTP GET to backend /api/samples/latest endpoint, handles 404 by returning null, maps response to GlucoseReading interface.

  async getLatestGlucose(userId: string): Promise<GlucoseReading | null> {
    try {
      const response = await this.client.get('/api/samples/latest', {
        params: {
          userId,
          type: 'BloodGlucose',
        },
      });
  
      const sample = response.data;
      return {
        value: sample.value,
        unit: sample.unit,
        date: sample.start_date,
        source: sample.source,
      };
    } catch (error: any) {
      if (error.response?.status === 404) {
        return null;
      }
      throw error;
    }
  }

• src/api-client.ts:3-7 (schema)

  Type definition for GlucoseReading, used as return type for getLatestGlucose and structure for response data.

  export interface GlucoseReading {
    value: number;
    unit: string;
    date: string;
    source: string;

• src/index.ts:57-71 (registration)

  MCP Tool registration in stdio server, defines name, description, and input schema for get_latest_glucose.

  {
    name: 'get_latest_glucose',
    description:
      'Get the most recent glucose/blood sugar reading for a user. Returns value, unit, timestamp, and source.',
    inputSchema: {
      type: 'object',
      properties: {
        userId: {
          type: 'string',
          description: `User identifier. Defaults to ${DEFAULT_USER_ID || 'configured user'} if not specified.`,
        },
      },
      required: [],
    },
  },

• src/index.ts:164-195 (handler)

  MCP tool call dispatcher in stdio server. Calls api.getLatestGlucose, handles null response, formats JSON output for MCP response.

  case 'get_latest_glucose': {
    const reading = await api.getLatestGlucose(userId);
  
    if (!reading) {
      return {
        content: [
          {
            type: 'text',
            text: 'No glucose readings found for this user.',
          },
        ],
      };
    }
  
    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify(
            {
              value: reading.value,
              unit: reading.unit,
              date: reading.date,
              source: reading.source,
            },
            null,
            2
          ),
        },
      ],
    };
  }

• src/http-server.ts:101-113 (registration)

  MCP Tool registration in HTTP SSE server.

  name: 'get_latest_glucose',
  description:
    'Get the most recent glucose/blood sugar reading for a user. Returns value, unit, timestamp, and source.',
  inputSchema: {
    type: 'object',
    properties: {
      userId: {
        type: 'string',
        description: `User identifier. Defaults to ${DEFAULT_USER_ID || 'configured user'} if not specified.`,
      },
    },
    required: [],
  },