Extend a trial

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

The description goes beyond annotations by explaining the mandatory two-call preview/execute flow, the refusal cases (no subscription or non-trialing status), and the exact structure of preview and executed responses. It clarifies the token-based confirmation mechanism that isn't evident from annotations or schema.

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 structured with a one-sentence purpose, a clear call-by-call breakdown, parameter list, and return formats. Every section earns its place; there is no filler.

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 stateful two-call tool with no output schema, the description fully covers all behavioral aspects: request flow, return shapes, validation constraints, and error conditions. This is a complete specification for the agent to invoke correctly.

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?

Though the schema already covers all four parameters, the description adds crucial context: confirm_token's role in the two-step flow, the day range, reason length, and the exact format for customer_id. It explains the meaning of omitting or passing the token, which the schema only hints at.

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 opens with a specific verb phrase 'Push a trialing subscription's end date out' and clearly states the resource (trial subscription) and action (extend by days). This clearly differentiates from siblings like harbor_issue_refund or harbor_run_query.

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 clearly states when the tool is applicable (trialing subscription) and provides refusal conditions, but it doesn't name any alternative tool for extending trials or handling non-trialing customers. The two-call protocol is described explicitly, which is helpful context.

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