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

No annotations are provided, so the description carries the full burden and discloses almost nothing: not whether message_blocks_json must be valid JSON, not what validation errors look like, not permissions or rate limits. The only behavioral hint is that a fallback notification path exists, and that comes from the parameter schema rather than the description.

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?

A single short sentence with the key differentiator (mobile Block Kit) front-loaded and no filler. It is efficient, though efficiency here borders on under-specification rather than tightness.

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 write tool with no annotations, no output schema, and two of three parameters undocumented, the description is far too thin. An agent cannot tell from it what a valid blocks payload is, what the reply contains, or how failures surface.

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?

Three parameters with only 33% schema coverage (only notification_message is documented in the schema). The description names message_blocks_json but gives no format expectations for it, and channel_id is undocumented in both places, so the description does not compensate for the coverage gap.

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 verb 'Post' and the payload format 'mobile Block Kit blocks' are stated, and parenthetically naming message_blocks_json hints at the intended alternative to the plain post_message sibling. However, the resource (a channel message) is only implied and the phrasing 'Post using' is grammatically vague about what is posted and where.

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?

There is no when-to-use guidance and no explicit contrast with the sibling post_message, even though mentioning 'mobile Block Kit' implies it is the rich-format alternative. An agent must infer from the name alone that this is the blocks-based counterpart.

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