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

Goes well beyond the annotations by disclosing cost ('may spend aisensy credit'), the WhatsApp 24-hour delivery constraint that determines whether a send will even land, and a mandatory human-approval gate tied to confirm=true. Annotations already cover destructive/non-idempotent, so the description is adding genuinely new operational context rather than restating hints.

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 highest-stakes facts (WRITE, sends, may cost credit), then the mode branch, then the confirmation protocol. Dense but every clause carries decision-relevant information; nothing is padding.

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 destructive, credit-spending mutation with no output schema, the description covers cost, delivery preconditions, and the approval workflow, which are the things an agent must know before calling. It omits what a successful send returns (message id) and any failure/rate-limit behavior, leaving a modest gap.

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 baseline is 3, but the description adds the conditional dependency between 'type' and the required companion fields (template_name, language_code, body_params), which the flat schema does not express. It doesn't add format detail for phone_number beyond the schema, so it sits just above baseline.

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 (send) and resource (WhatsApp message to a customer), then names the two mutually exclusive modes (free-text vs approved template) with the exact type value for each. An agent can distinguish this from campaign-sending siblings like aisensy_send_campaign_message purely from the description.

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 a concrete when-to-use rule for each mode: free text only inside the 24-hour window after the customer last wrote, otherwise an approved template. It does not explicitly route away from the campaign-sending siblings, so the alternative-selection guidance is strong but not complete.

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