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andygruening

Slack Message MCP

by andygruening

post_slack_message

Post a text message to a predefined Slack channel using a bot token.

Instructions

Post a message to the Slack channel configured by SLACK_CHANNEL_ID.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
textYesMessage text to post to Slack.
Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only states the action (posting) but does not mention any side effects, permissions required, rate limits, or error handling. This is insufficient 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.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, concise sentence with no extraneous information. It is well-structured and efficient.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple tool with one parameter and no output schema, the description is adequate. It explains the action and target. However, it could be improved by mentioning what happens on success or failure.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema covers the single parameter (text) at 100%. The description adds value by clarifying that the message is posted to a specific channel configured via environment variable, which aids understanding of the parameter's effect beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: to post a message to a specific Slack channel identified by an environment variable. The verb 'post' and resource 'message to Slack channel' are specific and unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No sibling tools exist, so differentiation is not needed. However, the description does not provide any usage context, such as prerequisites (e.g., ensuring SLACK_CHANNEL_ID is set) or when to avoid using this tool. Some guidance would be helpful.

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

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