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

Annotations already declare openWorldHint=true and readOnlyHint=false, so external reach is partly covered. The description still adds real value beyond that: email fallback for offline clients, the confirm-by-default behavior with an opt-out, and the required Cotlet API key with app access. It stops short of describing delivery failure or rate-limit behavior.

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 core action is front-loaded, but the text repeats itself: group delivery is described twice ('reaches each client individually' and 'in a group... individually'), and the confirmation requirement appears twice ('By default you confirm each call' and 'confirm with the user before each call'). Some sentences could be consolidated.

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 send-message tool with no output schema and openWorld annotations, the description covers the important operational facts: audience, delivery channel, confirmation policy, and auth requirement. Return/error details are not addressed but are less critical here.

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 100%, so client_id/group_name/body are already documented. The description reinforces the group behavior ('each client individually') but the schema already states that, so it adds little new parameter meaning over the baseline.

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 ('Message a client or every client in a group') and clarifies the group-vs-individual delivery semantics. It is clearly distinguishable from the sibling truecoach_list_messages reader, though it does not explicitly name that counterpart.

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 clear context for when to use it (messaging one client vs a group) and a confirmation precondition ('confirm with the user before each call' since it reaches other people). No explicit when-not or named alternative, but the operating conditions are well described.

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