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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the safety profile is covered. The description's only added behavioral context is the 'before it sends' constraint, which does usefully imply the call fails once a message is dispatched, but it does not say what happens to the record or what error/handling to expect.

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?

One short sentence, zero filler, with the scope constraint placed where it is read first. Appropriate size for a single-parameter cancellation tool.

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?

Simple tool with one fully documented parameter, rich annotations, and no output schema, so little is required. The description covers purpose and timing; only the post-send failure behavior and return shape are absent, which are minor given the annotation coverage.

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% with a single required parameter documented as 'Scheduled message id', so the schema carries the semantics. The description adds nothing about id format or where to obtain it, which is the correct baseline when coverage is high.

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?

States a specific verb+resource (cancel a scheduled message) and adds the scope qualifier 'before it sends', which distinguishes it from delete_message and get_scheduled_message. It does not explicitly name a sibling or contrast with delete_schedule, so it falls short of full differentiation.

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?

'Before it sends' implies the timing window in which this tool is the right choice, but the description never states what to do after a message has sent (e.g., use redact_message) or how it compares to delete_schedule. Usage must be inferred.

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