Cancel a pending scheduled message using its job ID. Retrieve the ID with list_scheduled_messages to avoid errors for already sent or nonexistent messages.
Cancel a pending scheduled message by its job ID. Use list_scheduled_messages to find the ID. Returns an error if the message was already sent or does not exist.
| Name | Required | Description | Default |
|---|---|---|---|
| job_id | Yes | Scheduled message job ID from list_scheduled_messages |
Changes observed during successful MCP inspections.
v1.33.3Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the behavioral burden. It discloses the key error cases: already-sent messages and nonexistent IDs. It does not describe the success return value or permission requirements, but for a simple cancellation operation the main behavioral expectations are covered.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences only: the first states the operation and key, the second explains how to find the ID and what errors to expect. Nothing is extraneous, and the most important detail is front-loaded.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a single-parameter utility with no output schema or annotations, the description provides the essential inputs, ID source, and error behavior. It stops short of stating what a successful cancellation returns, but that is reasonably inferable from the clear cancel action.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, and the schema already defines job_id as 'Scheduled message job ID from list_scheduled_messages.' The description reinforces this source but adds no new semantic details beyond the schema, so the baseline score of 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description uses a specific verb ('Cancel') with a precise resource ('pending scheduled message') and identifies the identifying key ('by its job ID'). This clearly differentiates the tool from siblings like schedule_message, list_scheduled_messages, and run_scheduled_messages.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description gives direct guidance on how to obtain the job_id ('Use list_scheduled_messages to find the ID') and sets an expectation by noting that cancellation fails if the message was already sent. It does not explicitly name alternatives or state 'use when the message is pending,' but the intent is clear enough.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.