Send WhatsApp Text Message

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

Annotations indicate it is not read-only (readOnlyHint=false) and not destructive (destructiveHint=false), which the description confirms by describing a send operation. The description adds transparency about rate limit delays and the CORE tier limitation, which goes beyond the annotations. No contradictions.

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 well-structured with clear sections for purpose, constraints, parameter details, and returns. It is efficient but not overly terse. Some information (e.g., parameter descriptions) partly duplicates schema, but overall it is concise and front-loaded with the main purpose.

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 input, behavior (rate limit, tier restriction), and output (status, messageId, contactId). Since there is no output schema, the description fills that gap. It also references sibling tools for lookup, making the context complete for a simple send operation.

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 the description partially overlaps with schema. However, the description adds value by explaining that contactId 'survives @c.us↔@lid flips' (not in schema) and clarifying replyTo's purpose. The schema already defines types and constraints, so the description enriches parameter understanding.

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'), the resource ('text message'), and the target ('contact (person or group)'). It distinguishes itself from sibling tools by specifying 'CORE tier supports text messages only', implying that other tools handle media. It also provides context for finding contact IDs via whatsapp_list_contacts.

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 clear usage context: send text messages, not media. It mentions rate limit delay, and provides guidance on how to obtain contactId and replyTo from other tools. It does not explicitly state when not to use, but the purpose is well-defined, and siblings like whatsapp_forward_message or whatsapp_download_media imply alternative use cases.

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