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

Annotations already declare readOnlyHint=false, destructiveHint=true, idempotentHint=false and openWorldHint=false, so the safety profile is covered structurally. The description adds nothing on top: it never mentions that message_type defaults, that private=true creates an internal note invisible to the contact, or that template_params switches to WhatsApp template delivery outside the 24-hour window. No contradiction, but zero added behavioral context.

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 text is short and front-loaded, but the second sentence is a pure restatement of the first with no new information. Every sentence should earn its place, and this one does not.

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 7-parameter, nested-object, multi-channel mutation tool with no output schema, the description is completely inadequate. It omits the private-note behavior, the WhatsApp template path and its 24-hour-window rationale, and the content_type variants, all of which materially affect correct invocation.

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 86%, so the schema already documents nearly all seven parameters, including the nested template_params semantics and content_type enums. The description contributes no parameter meaning at all, so the baseline 3 applies.

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 is a near-verbatim restatement of the tool title 'Create New Message' plus the phrase 'in the conversation'. It gives no distinguishing detail against siblings such as delete_a_message, list_conversation_messages, or new_conversation. This is the tautology case rather than a clear verb+resource statement.

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, no prerequisites (e.g. an existing conversation, inbox channel constraints), and no mention of alternatives. The agent must infer everything from the name alone.

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