send_message

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

With no annotations, the description carries the full burden. It discloses that sending is immediate and returns a success status, but says nothing about required auth, rate limits, whether the message is recallable, or what a failure looks like beyond a "status message"

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?

Front-loaded with the core action, then scoped parameter detail. The "Args:"/"Returns:" boilerplate is slightly redundant given a structured schema and output schema exist, but overall it is tight.

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?

An output schema exists, so the Returns block is superfluous, and the critical gaps are behavioral: no mention of authentication requirements, delivery semantics, or error conditions for a side-effecting messaging tool with zero annotation coverage.

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 0%, so the description must compensate — and it does, spelling out the recipient format in detail (country code, no '+' or symbols, JID forms for direct and group chats). The message parameter is left as just "message text", which is self-evident but not enriched.

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 ("Send a WhatsApp message") and narrows it to text messages by contrasting implicitly with siblings send_file and send_audio_message. The scope is unmistakable without opening the schema.

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?

It provides a conditional routing hint for group chats ("use the JID"), but never states when to choose this tool over send_file or send_audio_message, nor any prerequisites such as needing an authenticated session or known contact.

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