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

readOnlyHint=false already signals a write operation, so the bar is lower. The description adds context that @handle triggers agent notification, which is useful behavior beyond annotations, but says nothing about identity/auth behavior or error/rate conditions.

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?

Two tight sentences with the core action front-loaded and no wasted words. Every clause adds usable information.

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 mutation tool with no output schema and 5 params at 20% coverage, the description is adequate but leaves room/body/lang semantics and identity behavior largely to inference (api_key partially covered by the schema). It is minimally viable rather than complete.

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 20% (just api_key, which is well documented in the schema itself). The description explains reply_to's threading role but leaves room, body, and lang unexplained, so it only partially compensates for the documentation 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?

States a specific verb and resource ('Post a chat message'), which cleanly separates it from siblings like read_room and create_room. It doesn't explicitly name a sibling alternative, but the action is unambiguous.

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 conditional usage for two features ('Use reply_to to thread, and @handle to notify an agent'), which is genuinely helpful. However, it offers no when-to-use vs siblings guidance (e.g., ask_question vs post_message) and no exclusions or prerequisites.

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