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convertTimezone

Convert date and time between different timezones using IANA identifiers. Specify source and target timezones with an ISO 8601 date string to get formatted output.

Instructions

Convert date/time between timezones using Luxon

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
dateYesDate/time string to convert (ISO 8601 format)
fromTZYesSource timezone (IANA timezone identifier)
toTZYesTarget timezone (IANA timezone identifier)
formatNoOutput format (full, date, time, iso)full

Implementation Reference

  • The core handler function that parses the input date, converts timezone using Luxon, formats output based on specified format, and returns JSON-structured result.
    handler: async ({ 
      date, 
      fromTZ, 
      toTZ, 
      format = 'full' 
    }: { 
      date: string; 
      fromTZ: string; 
      toTZ: string; 
      format?: 'full' | 'date' | 'time' | 'iso' 
    }) => {
      try {
        const dt = DateTime.fromISO(date, { zone: fromTZ });
        
        if (!dt.isValid) {
          throw new Error(`Invalid date format or timezone: ${dt.invalidReason}`);
        }
    
        const converted = dt.setZone(toTZ);
        
        if (!converted.isValid) {
          throw new Error(`Invalid target timezone: ${converted.invalidReason}`);
        }
    
        let formattedOriginal: string;
        let formattedConverted: string;
    
        switch (format) {
          case 'full':
            formattedOriginal = dt.toLocaleString(DateTime.DATETIME_FULL);
            formattedConverted = converted.toLocaleString(DateTime.DATETIME_FULL);
            break;
          case 'date':
            formattedOriginal = dt.toLocaleString(DateTime.DATE_FULL);
            formattedConverted = converted.toLocaleString(DateTime.DATE_FULL);
            break;
          case 'time':
            formattedOriginal = dt.toLocaleString(DateTime.TIME_WITH_SECONDS);
            formattedConverted = converted.toLocaleString(DateTime.TIME_WITH_SECONDS);
            break;
          case 'iso':
            formattedOriginal = dt.toISO();
            formattedConverted = converted.toISO();
            break;
          default:
            throw new Error(`Unsupported format: ${format}`);
        }
    
        const result: TimezoneConversionResult = {
          originalDate: formattedOriginal,
          convertedDate: formattedConverted,
          fromTimezone: fromTZ,
          toTimezone: toTZ
        };
    
        return {
          content: [{
            type: 'text',
            text: JSON.stringify(result, null, 2)
          }]
        };
      } catch (error) {
        throw new Error(`Timezone conversion failed: ${error instanceof Error ? error.message : 'Unknown error'}`);
      }
    }
  • Input schema defining parameters for date, source/target timezones, and optional output format with validation rules.
    inputSchema: {
      type: 'object',
      properties: {
        date: {
          type: 'string',
          description: 'Date/time string to convert (ISO 8601 format)'
        },
        fromTZ: {
          type: 'string',
          description: 'Source timezone (IANA timezone identifier)'
        },
        toTZ: {
          type: 'string',
          description: 'Target timezone (IANA timezone identifier)'
        },
        format: {
          type: 'string',
          description: 'Output format (full, date, time, iso)',
          enum: ['full', 'date', 'time', 'iso'],
          default: 'full'
        }
      },
      required: ['date', 'fromTZ', 'toTZ']
  • TypeScript interface defining the structure of the timezone conversion result object used in the handler.
    export interface TimezoneConversionResult {
      originalDate: string;
      convertedDate: string;
      fromTimezone: string;
      toTimezone: string;
    }
  • src/index.ts:28-35 (registration)
    Registration of dateTimeTools (containing convertTimezone) into the central allTools object used by MCP server for tool listing and execution.
    const allTools: ToolKit = {
      ...systemTools,
      ...networkTools,
      ...geoTools,
      ...generatorTools,
      ...dateTimeTools,
      ...securityTools
    };
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions using Luxon but doesn't specify error handling (e.g., invalid timezone identifiers), performance characteristics, or what the output looks like. For a tool with 4 parameters and no output schema, this is a significant gap in transparency.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is extremely concise—a single sentence that directly states the tool's function without any fluff. It's front-loaded with the core purpose and uses minimal words, making it efficient and easy to parse.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity (timezone conversion with 4 parameters) and lack of annotations and output schema, the description is insufficient. It doesn't cover behavioral aspects like error cases, output format details beyond the schema's enum, or integration with sibling tools, leaving gaps for the agent to navigate.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema description coverage is 100%, so the input schema already documents all parameters thoroughly. The description adds no additional parameter semantics beyond what's in the schema (e.g., it doesn't explain Luxon-specific nuances). This meets the baseline for high schema coverage but doesn't enhance understanding.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: converting date/time between timezones using Luxon. It specifies the verb ('convert') and resource ('date/time between timezones'), making the function unambiguous. However, it doesn't explicitly differentiate from siblings like 'getCurrentTime' or 'listTimezones', which prevents a perfect score.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives. It doesn't mention scenarios where it's appropriate (e.g., for timezone conversions vs. getting current time with 'getCurrentTime') or any prerequisites. This lack of contextual direction leaves the agent to infer usage from the purpose alone.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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