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

Annotations already declare destructiveHint=true, so the bar is lower. The description adds real value beyond that flag by disclosing the reversibility boundary (only works before posting) and a confirm-with-user precaution. It doesn't cover success/failure behavior, but the added operational context is meaningful.

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?

Three tight sentences, front-loaded with the action, then the id source, then the safety caveat. No filler; each sentence carries distinct information.

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 destructive mutation with a safety annotation and no output schema, the description covers purpose, id sourcing, irreversibility, and a confirm step. It is complete enough to invoke correctly, with only minor gaps around result/error behavior.

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 coverage is 100%, so baseline is 3. The description reiterates that scheduled_message_id comes from list_scheduled_messages, which the schema already states, and adds no new syntax or format detail for account/channel. No added semantics beyond the schema.

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 pending scheduled Slack message) and even names the underlying Slack method (chat.deleteScheduledMessage). It clearly distinguishes itself from siblings like schedule_message and list_scheduled_messages by scoping to cancellation of a not-yet-posted message.

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?

Tells the agent where to get the required id (list_scheduled_messages) and defines the boundary condition ('before it posts', 'irreversible once the message has already gone out'), which implicitly excludes already-posted messages. It also instructs confirming the target with the user. It stops short of explicitly naming an alternative tool, so it's clear context rather than full when/when-not routing.

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