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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the mutation semantics are covered structurally. The description adds value beyond that with the permission model governing whose messages may be deleted, plus a note that the call returns confirmation or an error dict. It does not discuss irreversibility or side effects on chat history, keeping it below 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 plus Args/Returns blocks; the purpose and permission rules are front-loaded where an agent will read them. The explicit 'Args:'/'Returns:' scaffolding is slightly heavier than needed for a single-parameter tool but wastes little space.

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?

There is no output schema, and the description compensates by stating the return shape ('Confirmation on success, or error dict'). Combined with the permission rules and annotations that already mark the operation destructive, an agent has everything needed to invoke this correctly.

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?

With only one parameter, an integer message_id, and 0% schema description coverage, the schema itself explains nothing. The description's 'Args: message_id: ID of the message to delete' is effectively a restatement of the parameter name and adds no format, sourcing, or validation detail beyond what the schema already implies.

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 opening sentence gives a specific verb and resource ('Delete a family chat message'), which is unambiguous against siblings such as edit_family_chat_message, send_family_chat_message, and list_family_chat_messages. It stops short of explicitly naming those alternatives, so it earns a clear 4 rather than a 5.

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 supplies the operative precondition for use: 'Users can delete their own messages at any time; group owners and admins can delete anyone's messages.' This tells the agent when the call is authorized, which is genuine routing-relevant context, though it never contrasts this tool with the related edit/send/list chat siblings.

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