Build retargeting audience from prior engagement

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

Annotations indicate mutation and non-idempotency; description adds critical behavioral constraints (age requirement, minimum user count, region gate) and explains return format, going beyond annotation hints.

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?

Three sentences: front-loaded purpose, then key details, then return format. No redundant words; each sentence adds value.

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 5 parameters and no output schema, the description covers purpose, parameters, constraints, integration, and return format, making it fully self-contained for an agent.

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 covers 60% of parameters with descriptions; the description adds context for source_request_id (linking to prior message) and type (specifying default and click_url filter), though 'oa' parameter is not explained.

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: 'Create a LINE audience from people who clicked or opened a previous broadcast/narrowcast' and differentiates it from sibling tools like line_build_audience_from_csv by specifying the engagement source.

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 explicit guidance: when to use (retarget without CRM), constraints (source message ≥24h old, needs ~50+ users, region-gated), and how to integrate (feed audience into line_send_message).

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