send_imessage

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

The description states it sends an iMessage and returns success/error, but does not discuss failure conditions (invalid number, non-iMessage recipient), idempotency, or rate limits. With no annotations, this is moderate but incomplete.

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 extremely concise: one line for purpose, then a clear Args/Returns format. Every sentence serves a purpose without redundancy.

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 two-parameter tool with an output schema, the description covers purpose, parameters, and return type. However, it omits usage guidelines, edge case handling, and differentiation from siblings, which are needed for a complete understanding.

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?

The schema has 0% description coverage for parameters, so the description provides essential semantic value by explaining 'phone_number' (the phone number of the recipient) and 'message' (the message text). However, it lacks format constraints like country code requirements.

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 clearly states the action ('send') and resource ('imessage to someone in your contacts'), but does not explicitly differentiate from similar siblings like 'send_file_message' which also sends via iMessage. This reduces clarity when multiple sending options exist.

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?

No guidance is provided on when to use this tool versus alternatives (e.g., send_file_message, read_recent_messages). There are no prerequisites mentioned, such as requiring iMessage enabled or the recipient being an Apple ID.

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