Kalender Sync

Update event

update_event

Destructive

Updates an event. title, start and end describe the complete new state — including whether it is all-day: an event created all-day becomes a timed event if this call passes timestamps, and vice versa.

Two kinds of event are addressable:

Events THIS access created (via event_id from create_event) — always.
Any other event in a calendar the user allowed managing, visible in list_calendars as manageable: true. Their ids come from get_availability.

Four things are refused, and each says what to do instead — pass that on rather than retrying: • the calendar is not released for managing (the user can allow it per calendar) • it is shared at less than full detail (a setting, not a temporary error) • the event is a synchronised COPY — change the original in the named source calendar, the change reaches this one by itself • someone else organises it — call respond_to_event with response: "declined" and the same event_id instead

When the event has other participants, they are notified of the change by their calendar provider — mention that before moving it. The event_id of one date of a repeating appointment changes only that date.

Check status first: credits_exhausted means this call was NOT performed. Only warnings and credit information are returned in that case; no result data or write confirmation. Tell the user how to restore credits; do not retry automatically.

Input Schema

TableJSON Schema

Name	Required	Description
`end`	Yes	New end — same form as `start`; INCLUSIVE for all-day events.
`start`	Yes	New start — ISO 8601 with timezone (…+02:00 or …Z), or a bare date (2026-07-28) for an all-day event.
`title`	Yes
`all_day`	No	Force an all-day event; time components in start/end are discarded.
`event_id`	Yes	Identifier from create_event
`location`	No
`time_zone`	No	IANA zone, e.g. America/New_York. Preserves the named zone for timed events (so recurrences follow daylight saving) and decides the local day for all-day ones. Defaults to UTC.
`calendar_id`	No
`description`	No

Output Schema

TableJSON Schema

Name	Required	Description
`status`	Yes	ok: tool executed; use its result fields. credits_exhausted: not executed; no result fields.
`updated`	No
`event_id`	No
`warnings`	No
`resets_at`	No
`calendar_id`	No
`credits_required`	No
`credits_available`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedOct 18, 2026
- addedInput schema / properties / description / maxLength
```
Added value: +8000
```
- addedInput schema / properties / location / maxLength
```
Added value: +1000
```
- addedInput schema / properties / title / maxLength
```
Added value: +500
```

Changed6 schema fields changedOct 11, 2026

addedOutput schema / properties / credits_available
```
Added value: +{
+  "type": "number"
+}
```
addedOutput schema / properties / credits_required
```
Added value: +{
+  "type": "number"
+}
```

addedOutput schema / properties / resets_at

Added value: +{
+  "type": [
+    "string",
+    "null"
+  ]
+}

addedOutput schema / properties / status

Added value: +{
+  "description": "ok: tool executed; use its result fields. credits_exhausted: not executed; no result fields.",
+  "enum": [
+    "ok",
+    "credits_exhausted"
+  ],
+  "type": "string"
+}

addedOutput schema / properties / warnings

Added value: +{
+  "items": {
+    "type": "string"
+  },
+  "type": "array"
+}

changedOutput schema / required

Previous value: -[
-  "event_id",
-  "calendar_id",
-  "updated"
-]New value: +[
+  "status"
+]

Changed1 schema field changedAug 28, 2026

changedInput schema / properties / time_zone / description

Previous value: -"IANA zone deciding which local day an all-day event covers. Defaults to UTC."New value: +"IANA zone, e.g. America/New_York. Preserves the named zone for timed events (so recurrences follow daylight saving) and decides the local day for all-day ones. Defaults to UTC."

Changed4 schema fields changedAug 27, 2026

addedInput schema / properties / all_day

Added value: +{
+  "description": "Force an all-day event; time components in start/end are discarded.",
+  "type": "boolean"
+}

changedInput schema / properties / end / description

Previous value: -"New end, ISO 8601 with timezone"New value: +"New end — same form as `start`; INCLUSIVE for all-day events."

changedInput schema / properties / start / description

Previous value: -"New start, ISO 8601 with timezone (e.g. …+02:00 or …Z)"New value: +"New start — ISO 8601 with timezone (…+02:00 or …Z), or a bare date (2026-07-28) for an all-day event."

addedInput schema / properties / time_zone

Added value: +{
+  "description": "IANA zone deciding which local day an all-day event covers. Defaults to UTC.",
+  "type": "string"
+}

First observedJul 31, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations already declare destructiveHint=true and openWorldHint=true, so the mutation/external-visibility profile is partly covered. The description adds substantially beyond them: participant notification behaviour, that a synchronised copy must be changed at source, that editing one date of a recurrence affects only that date, and that on credits_exhausted no write occurs and only warnings/credit info are returned.

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?

Front-loaded with the one-line purpose, then organised into addressable-event types, refusal cases, and a status caveat — each block earns its place. It is dense and long for a single tool, but no sentence is pure padding and the bullets aid scanning.

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 9-parameter destructive mutation with an output schema, the description covers everything an agent needs to act correctly: which events are editable, the four failure modes and their alternatives, side effects on participants and copies, recurrence granularity, and the credits_exhausted no-op case. Return-value details are rightly delegated to the output schema.

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 only 56%, but the description compensates on the most consequential semantics: title/start/end represent the complete new state, and passing timestamps versus bare dates toggles all-day status. It also clarifies event_id provenance and that calendar_id must reference a manageable calendar. location, description and all_day still carry little or no explanatory text, keeping this short of a 5.

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?

States a specific verb and resource ('Updates an event') and immediately narrows scope by defining the two addressable event classes and naming the sibling tools that produce the relevant ids (create_event, get_availability, list_calendars, respond_to_event). An agent can distinguish this from create_event/delete_event/respond_to_event without opening any 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?

Explicitly enumerates when the call works (events this access created, or any event in a manageable calendar) and four refusal conditions with the prescribed alternative for each (not released, shared below full detail, synchronised copy, someone else organises it → respond_to_event). It also fronts the credits_exhausted status check so the agent knows the call may be a no-op.

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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