Send SMS — Premium (CIS / CN / MENA / Africa, Telnyx)

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

Annotations already indicate it is not read-only nor destructive. Description adds value by specifying per-message cost ($0.25), the 'default unknown prefix' behavior, and that it is the highest tier. No contradiction with annotations.

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?

Description is a single line with emojis and concise country lists. It front-loads the action and destination type, and includes cost and cross-reference. Could be slightly more structured, but efficient.

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?

Given output schema exists (not shown but stated), description doesn't need to cover return values. It provides price and verification tip. The complexity of the tool is moderate and description covers essential intent and cost implications.

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 schema descriptions fully cover all 4 parameters. The tool description adds no extra meaning beyond what is already in the schema. Baseline score of 3 applies.

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?

Description clearly states 'Send SMS to high-cost destinations' with specific country codes and regions. It distinguishes from sibling SMS tools (likely sms_na, sms_world) by specifying premium tier and covering unknown prefixes.

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?

Advises using telnyx.estimate_price to verify cost before sending, and implies it is for high-cost destinations only. Lacks explicit 'when not to use' but the list of countries and 'highest tier' signal appropriate context.

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