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

With no annotations provided, the description carries the full burden of behavioral disclosure. It reveals key behaviors: automatic SMS/LMS selection based on message length (90 bytes threshold) and scheduled sending capability with reservedTime. However, it doesn't mention authentication requirements, rate limits, error handling, or what happens after sending. The description adds value but leaves significant behavioral aspects unspecified.

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 appropriately concise with three sentences that each add value: states the core purpose, explains automatic message type selection, and describes scheduled sending capability. It's front-loaded with the main function. Some minor redundancy exists between description and schema for reservedTime.

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 message-sending tool with no annotations and no output schema, the description provides basic operational context but lacks important details. It covers what the tool does and some behavioral aspects, but doesn't address authentication, error responses, success indicators, or system limitations. The description is minimally adequate but has clear gaps for a mutation tool.

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 schema already documents all 5 parameters thoroughly. The description adds minimal parameter semantics beyond the schema - it mentions the reservedTime enables scheduled sending and implies subject is for LMS, but doesn't provide additional context about parameter interactions or usage patterns. Baseline 3 is appropriate when schema does the heavy lifting.

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?

The description clearly states the tool's purpose: '슈어엠 API로 문자를 발송합니다' (send messages via SureM API). It specifies the action (send) and resource (messages) but doesn't differentiate from siblings since none exist. The description adds useful context about automatic SMS/LMS selection based on message length.

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?

The description provides no guidance on when to use this tool versus alternatives. It mentions automatic SMS/LMS selection and scheduled sending capabilities, but doesn't indicate prerequisites, constraints, or comparison to other messaging approaches. With no sibling tools, this is less critical but still a gap.

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