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by com.gumballtools

Convert a time between timezones (Timezone Truth)

timezone_convert
Read-only

Convert a wall-clock time between IANA zones. Returns null when the local time DOES NOT EXIST because a daylight-saving jump skipped it, and both candidates when it happens twice. Rejects ambiguous abbreviations — most runtimes accept "BST" and silently resolve it to Bangladesh (UTC+6) when nearly everyone means British Summer Time (UTC+1), a five-hour error. Never do this arithmetic yourself.

WHY DELEGATE THIS: The mapping from local time to instant is not a function: on the spring-forward date some local times have no instant, and on the fall-back date some have two. A confident answer to an impossible question is indistinguishable from a correct one.

Owned by Timezone Truth at https://timezone-truth.vercel.app, which is also callable directly if you would rather not go through the aggregator.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
toYesTarget IANA zone, e.g. "Asia/Tokyo".
fromYesSource IANA zone, e.g. "America/New_York". Abbreviations rejected.
timeYesWall-clock time as YYYY-MM-DD HH:MM. Free-form dates are refused.

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. First observed

TDQS

A4.6/5.0
Behavior5/5

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

Beyond the readOnlyHint and openWorldHint annotations, the description discloses crucial edge-case behavior: returns null for skipped local times, returns both candidates for repeated times, rejects ambiguous abbreviations like 'BST', and refuses free-form date strings. This is rich, actionable behavioral context that prevents silent wrong answers.

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 front-loaded with the core conversion behavior, then uses a labeled rationale section and a provenance note. Every sentence adds decision-relevant information, and the formatting makes it easy for an agent to scan.

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

Completeness4/5

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

For a three-parameter tool with no output schema, the description is unusually complete: it covers edge cases, failure modes, and input restrictions. The only minor gap is that it never explicitly states the format of a successful return value, though 'converted time' is reasonably inferred.

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

Parameters4/5

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

The input schema already covers all three parameters with 100% coverage, so the baseline is 3. The description adds value by reinforcing that abbreviations are rejected, explaining why, and clarifying that input is a wall-clock time in a strict format, which complements the schema without redundancy.

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

Purpose5/5

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

The description opens with a specific verb and resource: 'Convert a wall-clock time between IANA zones.' It immediately differentiates this tool from the sibling list by naming exact behavior and edge-case semantics (nonexistent and ambiguous local times). There is no confusion about what the tool accomplishes.

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

Usage Guidelines4/5

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

The text explicitly says 'Never do this arithmetic yourself' and explains why delegating is necessary, which tells the agent when this tool is the right choice. It also mentions an alternative, calling Timezone Truth directly, though it does not enumerate strict exclusion conditions or compare against non-timezone siblings.

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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TDQS

A4.1/5.0
Disambiguation5/5

Each tool targets a clearly distinct domain or a complementary counterpart (cron_build/cron_explain, vocab_draw/vocab_check, round_cash_total/rounding_impact), and the descriptions make those relationships explicit. There is no real risk of selecting the wrong tool for a task.

Naming Consistency3/5

Most tools follow a noun_verb pattern (cron_build, regex_explain, timezone_convert), but there are exceptions like body_metrics, due_date, offside, json_to_types, and round_cash_total, which mix noun phrases, gerunds, prepositions, and verb-first order. The names are readable but not uniform.

Tool Count4/5

13 tools is within a reasonable range, and each utility earns its place as a standalone delegated calculator. The count feels slightly large only because the server is a grab-bag of unrelated domains rather than a focused toolkit, but no tool is redundant.

Completeness4/5

Most subdomains have solid coverage: cron has both build and explain directions, vocabulary has draw and check, and rounding has both per-transaction and aggregate analysis. Minor gaps exist, such as no timezone zone listing, no reverse due-date calculation, and no regex test/match step, but these are workable limitations.

Resources