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

With no annotations, the description carries the full burden; it does disclose two real behavioral constraints – an Advance plan key is required and the template must already be approved. It says nothing about rate limits, whether the send is immediate or queued, what happens on unapproved templates, or what the response returns.

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?

Two short sentences, front-loaded with the plan requirement and then the action plus the pre-step. Every clause carries information; no filler.

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 3-parameter send tool with no annotations and no output schema, the definition covers the essential prerequisite path but leaves gaps: no indication of what a successful send returns (message ID, status), delivery behavior, or failure modes for invalid numbers or unapproved templates.

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 'to', 'template', and 'variables' are already documented, and the baseline is 3. The description adds only a light hint that variables must match the template's expected values via the list_templates step; it does not explain the object-vs-array shape of 'variables' or the phone number format.

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 an approved WhatsApp template') with the key qualifier that only approved templates may be used. It names list_templates as the way to find template names, which distinguishes it from that sibling, though it does not contrast with create_template.

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?

Gives an explicit prerequisite workflow: 'call list_templates first to confirm the template name and variables.' It also states the plan requirement. It stops short of saying when not to use it (e.g., free-form/non-template messages), so no exclusions.

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