Calcgrid

IANA Local Time Resolver

resolve_local_time

Read-onlyIdempotent

Use this when you must safely turn a named-zone local time into an instant, validate a scheduled time around a daylight-saving transition, or preserve every possible interpretation instead of silently choosing one. Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery.

Do not use this when the input already includes a numeric UTC offset or Z, the task only needs the current clock time, or latitude/longitude must first be mapped to a zone. What it computes: Resolves a local wall-clock time with pinned IANA tzdb 2026d. Returns every valid UTC candidate for a repeated fall-back time, or the exact gap and shift-forward suggestion for a nonexistent spring-forward time. Example user requests: Resolve 2026-11-01 01:30 in America/New_York and return both UTC candidates. | Does 2026-03-08 02:30 exist in New York? Show the DST gap. | 判断 Australia/Adelaide 的 2026-10-04 02:30 是否存在，并给出时区数据版本。 Inputs: local_datetime (string); time_zone (string). Complete JSON argument examples: {"local_datetime":"2026-11-01T01:30:00","time_zone":"America/New_York"} | {"local_datetime":"2026-03-08T02:30:00","time_zone":"America/New_York"} Outputs: local_datetime, time_zone, resolved_zone_id, status, candidate_count, candidates, gap, related_transition, previous_transition, next_transition, tzdb_version, dataset_version, source_url, source_sha256, coverage_note. Formula: for each zone offset o: candidate_utc = local_wall_time + o; keep candidates whose active offset at candidate_utc equals o Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/local-time-resolver with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/time/local-time-resolver.md

Input Schema

TableJSON Schema

Name	Required	Description	Default
`time_zone`	Yes	IANA zone identifier present in tzdb 2026d.
`local_datetime`	Yes	Wall-clock date and time without Z or a numeric offset; it will be interpreted only in time_zone.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`links`	No
`result`	Yes
`request`	Yes
`sources`	No
`success`	Yes
`version`	No
`freshness`	No
`timestamp`	Yes
`next_actions`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 26, 2026

addedInput schema / examples

Added value: +[
+  {
+    "local_datetime": "2026-11-01T01:30:00",
+    "time_zone": "America/New_York"
+  },
+  {
+    "local_datetime": "2026-03-08T02:30:00",
+    "time_zone": "America/New_York"
+  }
+]

AddedSep 26, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Beyond the annotations declaring readOnly/idempotent/non-destructive, the description discloses rich behavior: every valid UTC candidate for ambiguous fall-back times, exact gap and suggestion for nonexistent spring-forward times, pinned tzdb 2026d, the underlying formula, and a direct REST fallback. No contradiction with annotations.

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

Conciseness4/5

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

The description is well-structured and front-loaded with usage guidance, making key information easy to find. However, it is long and somewhat redundant, listing output fields and the formula even though an output schema already exists.

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

Completeness5/5

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

The description fully covers when to use, when not to use, input construction, output behavior, algorithm, REST fallback, documentation, and example requests. With an output schema present, nothing an agent needs to call it correctly is missing.

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?

Schema coverage is 100%, so the baseline is 3. The description adds value by emphasizing that local_datetime must be wall-clock time without Z/offset, providing complete JSON examples, and linking both parameters via the resolution formula.

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 states a specific action: resolving a local wall-clock time in a named IANA zone into UTC instant(s). It clearly differentiates the tool from siblings by noting it is not for inputs with numeric offsets/Z, current-time-only tasks, or lat/long mapping.

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

Usage Guidelines5/5

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

It begins with explicit 'Use this when' scenarios and follows with a 'Do not use this when' exclusion list, giving the agent clear decision criteria. It also instructs the agent to call the tool directly instead of computing from memory, which is strong usage guidance.

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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