Kalender Sync

Create a calendar sync

create_sync

DestructiveIdempotent

Creates a sync between two of the user's own calendars — one-way (source into target) or two-way (both directions, one sync) — after the user confirmed this specific source, target, direction and detail level(s) in the chat. Call preview_sync first and tell the user what it reports. The same checks run again here, so a preview does not guarantee success.

Pass a stable request_id: the same id with the same parameters returns the same sync instead of creating a second one, and the same id with different parameters fails rather than silently creating another.

The result is created_pending_processing: the sync exists and copying starts in the background; nothing is synchronised yet, so the target may look empty for a few minutes. The sync then keeps running: it creates, updates and removes its own copies in the target as source events change. It keeps running even after this assistant's access is revoked.

For two-way, both calendars must be shared with this access and released for syncs; each direction has its own detail level (reverse_detail_level, default detail_level), and both legs are created together or not at all.

event_colors keeps each event's own color in the copies (Google colors, Outlook categories, CalDAV COLOR). Omitted, it is on for directions with more than busy_only and off for busy_only, as in the app. For Outlook the colors are Outlook categories named after the color; the category names and, where Microsoft asks for it, the permission to create categories are handled in the app (syncs_url) — without that permission the sync runs in the calendar color. Apple Calendar shows no per-event colors at all.

Syncs with other people, changing rules and reversing direction are not available here — that happens in the Kalender Sync app, linked as syncs_url. Deleting works with preview_delete_sync and delete_sync. Costs no credits.

Input Schema

Name	Required	Description
`direction`	No	Default one_way. Ask the user.
`request_id`	Yes	Stable id for this request; reuse it when retrying the same call
`detail_level`	Yes	How much of each event reaches the target: busy_only (a blocker without details), title_and_time, or full_details. Ask the user; do not assume. At most max_detail_level from preview_sync.
`event_colors`	No	Keep event colors in the copies (all directions). Default: on unless the direction is busy_only.
`source_calendar_id`	Yes	Calendar whose events are copied
`target_calendar_id`	Yes	Calendar the copies are written into
`reverse_detail_level`	No	Two-way only: detail level from target back into source. At most max_reverse_detail_level.

Output Schema

Name	Required	Description	Default
`legs`	Yes
`status`	Yes
`replayed`	Yes
`direction`	Yes
`syncs_url`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 24, 2026

addedInput schema / properties / event_colors

Added value: +{
+  "description": "Keep event colors in the copies (all directions). Default: on unless the direction is busy_only.",
+  "type": "boolean"
+}

AddedOct 18, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Goes well beyond the annotations: it discloses that the result is created_pending_processing with nothing copied for a few minutes, that the sync keeps mutating the target afterward and survives revocation of assistant access, that two-way legs are all-or-nothing, and that the cost is zero credits. The destructiveHint is substantiated by explaining that the sync removes its own copies in the target and that deletion is handled by delete/delete_sync instead.

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?

Every paragraph carries distinct information (precondition, idempotency, lifecycle state, two-way rules, colors, out-of-scope) and the purpose is front-loaded. It is on the long side, and the Outlook category-name and Apple Calendar color detail is close to vendor trivia an agent rarely needs mid-call.

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?

For a mutating, open-world, idempotent tool with an output schema, the description covers the remaining burden: preconditions, the returned status value, post-call lifecycle, failure atomicity for two-way, and where the unsupported operations live. Nothing an agent needs in order to invoke it correctly is missing.

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

Parameters5/5

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

Though schema coverage is 100% (baseline 3), the description adds semantics the schema cannot: request_id replayed with identical parameters returns the same sync while a reused id with different parameters fails rather than duplicating work, and reverse_detail_level defaults to detail_level with both legs created atomically. event_colors defaults are spelled out per direction and per calendar platform.

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 first sentence names a specific verb (creates a sync) and resource, and explicitly scopes it to the user's own calendars, one-way or two-way. It distinguishes itself from siblings by naming preview_sync, preview_delete_sync, delete_sync and syncs_url, so an agent can pick it without opening another schema.

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?

Gives an explicit precondition chain: user must have confirmed source, target, direction and detail level(s), and preview_sync must be called first with its result relayed. It also names what this tool cannot do (syncs with other people, changing rules, reversing direction) and routes those to the Kalender Sync app, which is a genuine when-not clause.

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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