Send an SMS, MMS or RCS message

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

Far exceeds what the annotations convey. It discloses real-world side effects (each recipient becomes its own message and is billed), the approval/auth gate, opt-out refusal behavior ('refused by Vobiz (opted_out)'), the status lifecycle (scheduled/sent/delivered/failed) and where to observe it, and how idempotency replay behaves. The destructiveHint and idempotentHint annotations are consistent with, and enriched by, this text.

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 endpoint and the four required fields, then behavioral notes — good ordering. It is dense and semicolon-heavy in a single paragraph, which slightly hurts scannability, but essentially every clause carries operational information.

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 14-parameter mutation tool with no output schema, the description covers requirements, costs, opt-out handling, scheduling semantics, delivery-receipt follow-up, and idempotency — everything an agent needs to invoke it correctly and safely.

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 baseline is 3, but the description adds genuine meaning: `to` is per-recipient and billed individually, `from` varies by channel, `confirm` is an approval gate rather than a plain boolean, and `idempotency_key` replay semantics are spelled out. Remaining parameters (dlt_*, media_urls, scheduled_at, tag, title) are left to the schema.

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+resource ('Send a real SMS, MMS or RCS message through Vobiz') and even the underlying endpoint POST /api/v1/sms/messages. It is clearly distinguishable from siblings like list_messages, get_message, and preview_message_cost, which are named for the roles they play relative to it.

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?

Explicitly names the prerequisite flow: 'Use preview_message_cost first to show the price and segment count' and requires 'confirm: true' only after the user approved the exact sender, recipients and text. It also gives the channel-conditioned rule for choosing `from` and the alternative path for checking delivery (get_message).

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