send_message

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

No annotations are provided, so the description bears the full burden of behavioral disclosure. It mentions that the tool can send to phone numbers or email addresses, but does not explain delivery behavior, error handling, message limits, or whether iMessage automatically falls back to SMS. This leaves significant behavioral ambiguity for a send operation.

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 a single, front-loaded sentence with no filler. Every word contributes to explaining the tool's core function, making it highly efficient.

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 tool with 3 fully documented parameters and no output schema, the description covers the essential function but omits practical details like return behavior, error cases, or whether SMS can truly be sent to an email address. The potential ambiguity about iMessage/SMS delivery to email prevents a higher score.

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 100%, so the schema already documents all parameters (to, text, service) clearly. The description adds no new parameter meaning beyond restating that recipients are phone numbers or email addresses, which is already in the schema. Baseline of 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 clearly states the verb 'send' and the resource 'iMessage or SMS' with recipient types. It is immediately distinguishable from all sibling tools (list_chats, get_chat_messages, search_messages, get_chat_participants), which are read-oriented.

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 implies the tool's purpose through the verb 'send', so an agent can infer that it is for sending messages rather than listing or searching. However, it does not explicitly state when to use this tool versus alternatives, nor does it offer any exclusions or fallback guidance.

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