@mnicole-dev/calcom-mcp-server

cancel-booking

Cancel a scheduled booking by providing its unique UID. Optionally include a cancellation reason to document why the booking was removed.

Instructions

Cancel a booking by its UID.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "bookingUid": "<bookingUid>"
    },
    "name": "cancel-booking"
  }
}

Input Schema

Name	Required	Description	Default
`bookingUid`	Yes	The booking UID to cancel
`cancellationReason`	No	Reason for cancellation

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Aug 30, 2026

TDQS

B3.3/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full disclosure burden. 'Cancel a booking' signals a mutating action, but it does not explain side effects such as irrevocability, notifications, downstream schedule updates, or required permissions. This is a meaningful gap for a destructive operation.

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 a single, front-loaded sentence with no filler. Every word contributes meaning, and the essential action and identifier are immediately clear. This is appropriate conciseness.

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

Completeness3/5

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

For a simple two-parameter tool with fully documented parameters and no nested objects, the description plus schema is mostly adequate for invoking the tool correctly. However, with no annotations and no output schema, the description does not explain cancellation consequences or response behavior, leaving the context somewhat incomplete for an agent deciding whether cancellation is safe or reversible.

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

Parameters3/5

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

Schema description coverage is 100%, so the input schema already documents both bookingUid and cancellationReason. The description only reinforces that the booking is identified by UID and adds no new parameter semantics. Baseline 3 is appropriate because the schema does the heavy lifting.

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 states a specific action ('Cancel') and resource ('a booking') plus the key identifier mechanism ('by its UID'). It is clear and readable. It does not explicitly distinguish itself from sibling tools like decline-booking or confirm-booking, so it misses the top score.

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 phrase 'by its UID' implies this tool should be used when the agent has a booking UID and wants to cancel it. However, no explicit when-to-use vs alternatives guidance is provided, and no mention of not using this for declining, rescheduling, or confirming bookings. The usage context is only implicit.

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