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

Annotations already declare this is a non-read-only, open-world, idempotent, destructive action. The description adds meaningful context beyond the annotations: the message is sent on the person's behalf and the recipient is told it came via an AI agent. It still does not describe irreversibility or failure behavior, so it stops short of a 5.

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 short sentences with no wasted words. The core action and scope are front-loaded, and the AI-disclosure note is a useful second sentence.

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 three-parameter message-sending tool with rich annotations and a fully documented schema, the description covers purpose and key behavioral context. It lacks explicit return/failure information, but no output schema exists, so the remaining gap is minor.

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 description coverage is 100%, so all three parameters are well documented in the input schema. The description reinforces the chat_id/room concept but adds no additional parameter-level semantics, making the baseline 3 appropriate.

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 states a specific verb ("Write") and resource ("the person's private chat (room chat_id)"), making the action clear. It does not explicitly distinguish this tool from sibling message-sending tools such as event_application_message, so it falls short of the top score.

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 implies usage by saying it writes in the person's private chat, but it gives no explicit when-to-use guidance, prerequisites, or alternatives. With many sibling tools available, an agent must infer the selection context.

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