Preview SMS template

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

Annotations declare readOnlyHint=true, and description does not contradict. Description adds transparency by specifying return values (plain-text body, missing variables, segment estimate) and that it does not send. No mention of errors or limitations, but sufficient for read-only.

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?

Extremely concise: one main sentence plus a clarifying sentence. No wasted words, front-loaded with purpose.

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 read-only preview tool with 3 params and no output schema, the description covers key return values and behavior. Could mention error cases or prerequisites, but adequate for typical use.

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 67% (variables and bodyTemplate have descriptions). Tool description does not add new meaning beyond schema for these params, and templateKey is not further explained. Baseline 3 is appropriate as schema handles most semantics.

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 specifies the action (render, return body, missing variables, segment estimate) and explicitly states it does not send. Distinguishes from sending tools like send_transactional_sms.

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?

Description states what the tool does and that it doesn't send, but lacks explicit guidance on when to use over siblings like render_template or compose_template. Could add context like 'Use to preview before sending'.

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