Intervals.icu MCP Server

Update a calendar event

update_event

Idempotent

Update a calendar event by moving it to a different date, renaming it, or rewriting its workout steps, changing only the fields you provide.

Instructions

Change a calendar event: move it to another date, rename it, or rewrite the workout steps. Only the fields you pass are changed. Confirm the change with the user first.

Workout text syntax (Intervals.icu): one step per line starting with "- ", e.g. "- 10m Z2 Pace", "- 1.5km 7:00/km Pace", "- 90s 85% Pace", "- 10m Ramp 60-80% HR", "- 5m Z2 HR". Durations: 30s, 90s, 1m30, 10m, 1h. Distances: 400mtr (meters!), 1.5km, 2mi — "400m" means 400 MINUTES. Repeats: a line ending in "Nx" (e.g. "Main set 4x") followed by its steps, then a blank line. Section lines like "Warmup"/"Cooldown" are labels. Text before the duration labels a step ("- Strides 20s Z5 Pace"). Power (rides): "75%" (of FTP), "200w", "150-180w", "Z2". Bpm ranges like "140-150bpm" are NOT supported; use HR zones or % HR.

Input Schema

TableJSON Schema

Name	Required	Description
`id`	Yes	Event id (from list_events).
`date`	No	Move to this date.
`name`	No
`time`	No	Start time "HH:MM" (optional).
`type`	No	Sport, e.g. "Run", "Ride", "Walk". Required for workouts and races.
`indoor`	No
`category`	No
`duration`	No	Planned duration ("45:00" or seconds) when there are no workout steps.
`end_date`	No	Last day for multi-day entries (holiday, sick, …).
`description`	No	For workouts: the steps in workout text syntax. Otherwise free-text notes.
`distance_km`	No	Planned distance in km.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`event`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.0.0Sep 26, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already mark the tool as non-read-only, idempotent, and non-destructive. The description adds meaningful behavioral context beyond that: only passed fields are changed, user confirmation is required, and the workout description parameter has a strict syntax with edge cases like '400m' meaning minutes. 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.

Conciseness5/5

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

The description is front-loaded with the core action and confirmation requirement, then moves into a dense but necessary syntax reference. The long second paragraph earns its place because it documents a complex parameter format with examples and edge cases; there is no filler.

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?

Given the 11-parameter schema, the output schema, and the annotations, the description is complete enough for an agent to invoke the tool correctly. It covers the partial-update behavior, the user-confirmation requirement, and the one truly complex parameter (workout text syntax). Remaining parameter details are already present in the 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?

With 73% schema coverage, the schema already documents most parameters. The description adds critical meaning for the description parameter by fully explaining workout text syntax, units, repeats, and unsupported bpm ranges, and it clarifies that all optional parameters only apply when explicitly passed.

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 opens with a specific action and resource: 'Change a calendar event', then lists concrete operations (move date, rename, rewrite workout steps). It clearly conveys partial-update semantics, but it does not explicitly differentiate this tool from siblings like update_workout or create_events, so it stops short of a 5.

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

Usage Guidelines3/5

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

The description provides an operational guideline: 'Confirm the change with the user first', and implies use when modifying an existing calendar event. However, it never states when to prefer this tool over update_workout or create_events, nor does it give exclusions or alternative routing.

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