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

The description goes well beyond the destructiveHint annotation by disclosing that the call actually schedules delivery, describes the required OAuth scopes, explains public-vs-private channel invite requirements, and instructs the agent to confirm target, text, and time before calling. These are exactly the behavioral details an agent needs for a mutation tool.

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?

The description is front-loaded with the core purpose, then layers in parameter syntax, workspace selection, permissions, and a pre-call confirmation rule. Every sentence earns its place despite the length, and there is no filler.

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 scheduling tool with no output schema and only sparse annotations, the description covers the necessary call semantics, prerequisites, channel constraints, and a safety confirmation. Nothing essential to correct invocation is missing.

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%, so all five parameters are already documented in the schema. The description mostly repeats those parameter meanings, adding only the useful pointer to list_accounts for the account parameter; the baseline of 3 is appropriate when structured fields already carry the semantic load.

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 states a specific verb and resource: 'Schedule a Slack message to post later', and pairs it with the underlying API method. The future-delivery framing clearly distinguishes it from send_message and other Slack messaging siblings without needing to name them.

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?

It gives clear context for when to use the tool (posting later) and states important prerequisites for account selection and channel permissions. It stops short of explicitly naming alternatives such as send_message or cancel_scheduled_message, so it does not reach the top usage-guidance tier.

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