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

Annotations already declare the safe read profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true). The description adds meaningful context beyond that: ordering (oldest first), text-only content excluding images/files, the checkout-based open/read-only lifecycle, and the Cotlet API key auth requirement.

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 front-loaded with the core purpose and return format, and every sentence carries information. There is mild redundancy, as the open/read-only state is stated in the first sentence and restated in the third, which slightly dilutes the 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 simple one-parameter read tool with no output schema, the description fully carries the load: it explains what is returned and in what order, excludes non-text content, describes the lifecycle state, and notes the auth requirement. Nothing needed to invoke it correctly is missing.

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?

There is a single parameter with 100% schema description coverage, so the schema already documents chat_id and its origin (from list_chats). The description adds no further format or constraint detail, 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 and resource (get the messages of one guest chat) and clearly separates this from the list/send siblings by describing a single chat retrieved by chat_id. It also conveys the return shape (oldest-first text) and the chat's open/read-only lifecycle state, which sharpens what the tool actually returns.

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?

Usage context is clear: this retrieves one chat identified by chat_id, and the schema ties discovery to list_chats. It does not, however, explicitly name alternatives (e.g. list_chats vs get_chat vs send_chat_message) or state when-not-to-use, so it stops short of full routing guidance.

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