Post Slack Message

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

The description adds behavioral context beyond annotations: it specifies that messages are sent as the user (not a bot), supports Slack mrkdwn formatting, can post as a thread reply, and returns a confirmation with timestamp and channel. This complements the annotations (readOnly=false, idempotent=false) without contradicting them.

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 concise and well-structured with Args and Returns sections. Every sentence contributes useful information: purpose, parameters, and return value, with no redundancy or padding.

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 simple 3-parameter tool with full schema coverage and informative annotations, the description covers purpose, parameter semantics, and return value. It provides sufficient context for an AI agent to select and invoke the tool correctly without missing critical information.

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?

The input schema already has complete descriptions for all three parameters (100% coverage). The description adds minor examples (e.g., channel ID format) and clarifies the thread behavior, but it largely mirrors the schema, providing only marginal added value beyond the structured data.

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 uses a specific verb ('Post') and resource ('Slack channel or DM'), and explicitly states it posts as the user account. This clearly distinguishes it from sibling tools that are all read/search oriented.

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?

The description makes the tool's purpose clear, and given that all sibling tools are read-only, it is obvious this is the tool for sending messages. However, it does not explicitly mention alternatives or provide when-not-to-use guidance, so it doesn't fully meet the 'explicit alternatives' bar.

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