slack_send_message

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

Goes well beyond annotations by specifying that nothing is appended (no signature, footer, blocks, or attribution), that user authorization is a precondition, and that retries after uncertain outcomes are dangerous — context the idempotentHint=false flag only hints at. These are the exact failure modes for a messaging 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?

Three tight sentences, front-loaded with the core action, followed by authorization and retry constraints. No filler or restatement of the tool name.

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 auth/retry guidance is valuable, but with no output schema the description never says what is returned (e.g., the message ts needed for threading or permalinks), and it leaves six of eight parameters undocumented. Adequate for a safe send, incomplete for correct invocation of threading and formatting options.

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 only 38%: thread_ts, mrkdwn, parse, unfurl_links, unfurl_media, and reply_broadcast have no documentation in either the schema or description. The description clarifies the 'text' semantics (exact body, no blocks) but leaves half the parameters, including threading and link unfurling, unexplained.

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 and resource ('Send the exact supplied message body to an authorized Slack channel or DM') with clear scope that separates it from read/search siblings. It never names slack_edit_message, so an agent must infer that this tool creates new messages rather than modifying existing ones.

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?

Gives explicit gating conditions — only send when the user authorized content and destination — plus a caution against blind retries after an uncertain result. It does not name alternatives (e.g., use slack_edit_message to revise an already-sent message), which would have taken this to a 5.

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