slack_send_message

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

With no annotations provided, the description carries the full burden, and it excels: it discloses the default 3-minute scheduling delay, the cancellation window, the ability to post immediately with SLACK_ADD_MESSAGE_DELAY=0, and the exact return payload. An agent would not be surprised by the tool's side effects.

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 tightly structured with a behavior paragraph, argument list, and return section. Every sentence contributes useful information, and the most important behavioral caveat (scheduling delay) 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?

The description covers behavior, parameters, returns, and the related cancellation tool. There is an output schema, but even without it the agent has enough to call the tool correctly and understand the result.

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 0%, but the description compensates fully by explaining channel_id (C/D/G prefix), text (Markdown supported), and thread_ts (parent message timestamp for threaded replies). Every parameter receives meaningful semantic context beyond the raw JSON 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?

The opening sentence 'Send or schedule a Slack message' uses a specific verb and resource, and the scheduling/cancellation details distinguish it from sibling read-only Slack tools. There is no ambiguity about what the tool does.

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 provides clear context for how the tool behaves, including the scheduling delay and how to cancel via slack_cancel_scheduled_message. It does not explicitly state when not to use this tool, but no sibling send tool exists so the guidance is sufficient.

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