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

Annotations already mark the tool as non-read-only and destructive. The description adds behavioral value by explaining native rendering support caveats and the WhatsApp multi-attachment-to-separate-messages behavior, which is not visible in the schema or annotations. It could go further in specifying which providers support native rendering, but the added context is meaningful.

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 concise and front-loaded with the core action. The three sentences each add useful information, though 'native media' in the third sentence is somewhat redundant with the first sentence. Overall it is appropriately sized and readable.

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?

The description covers purpose and a key provider-specific nuance, but it omits essential invocation details such as the format of content_base64, the role of content_type and filename, and what response or outcome to expect. With no output schema and low parameter coverage, these omissions leave the agent under-equipped for correct calls.

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 only 33%, so the description must compensate, but it does not explain the key parameters content_base64, content_type, filename, or text. It only implies that these relate to a media/file attachment. The agent is left guessing about base64 encoding format, MIME type expectations, and whether text is a caption. This is a significant gap.

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 one media/file attachment using the provider's native rendering mode where supported.' This distinguishes it from text or voice messaging tools by emphasizing media, native rendering, and one-attachment-per-call behavior. However, it does not explicitly name or contrast any sibling tool.

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 gives useful context: 'Resolve chat_id first' is a prerequisite, 'Useful for inline image/video/native media' identifies a use case, and the WhatsApp note explains when and why to prefer this tool for predictable one-attachment behavior. It does not explicitly mention alternatives or state when not to use it.

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