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

Annotations already indicate this is a mutating, non-idempotent operation, and the description adds genuinely useful behavioral context: channel fallback order, scheduling, typing simulation, delivery callbacks, and the resulting delivery ID. It clearly explains recipient selection rules across channels, which goes beyond what the annotations alone convey.

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 compact and front-loaded: the first sentence summarizes capabilities, the second gives usage guidance, and the third covers recipient edge cases and return value. Every sentence contributes distinct information without redundancy or 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?

Despite having 14 parameters and no output schema, the description covers the essential contextual gaps: when to use it, what channels are involved, how recipient identification works, and what the tool returns (delivery ID for get_delivery_status/delete_delivery). The rich per-parameter schema descriptions handle the remaining details, so nothing critical is missing.

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 the baseline is 3, but the description adds important relational semantics: phone is required except for tdlib (username/tdlib_user_id) and WhatsApp (whatsapp_lid). It also explains dispatch_routing as an ordered cascade and clarifies the meanings of channel names beyond the enum labels.

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 ('text message') with an explicit list of supported channels and a cascade fallback behavior. It explicitly differentiates from siblings by calling out send_bulk for many phone numbers and send_file for media, so an agent can tell them apart immediately.

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?

Provides an explicit when-to-use rule: 'Use it when the user asks to text, message, notify or reply to one person or group chat.' It also names the alternatives for other cases ('For many phone numbers use send_bulk; for documents, images, audio or video use send_file'), leaving no ambiguity about routing conditions.

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