Pay: trial status

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavior by explaining that the trial length is not set directly but is derived as the longest trial among active subscription plans, and that the plan is named; it does not discuss auth or error behavior, which keeps it short of a 5.

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?

Four sentences, front-loaded with the purpose, then progressively explaining scope, derivation, and mutation alternatives. Each sentence earns its place with 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?

No output schema exists, so the description must convey what is returned; it does so by stating the enabled flag, the derived length, and the named source plan. For a simple zero-parameter read tool with read-only annotations, nothing material is missing.

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?

The tool takes no parameters, so there is nothing for the description to clarify beyond the schema. The baseline for a zero-parameter tool is 4.

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 states a specific verb-and-resource ('Show whether the trial is enabled and its derived length') and explains exactly what is reported, including that the length comes from the longest active subscription plan. It distinguishes itself from the mutating siblings `pay_trial_enable`, `pay_trial_disable`, and `pay_plans_update`.

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?

It clearly frames this as the read-only inspection tool and names the alternative tools for changing trial state. It does not state a negative condition or when not to use it, but for an empty-schema read sibling the routing is clear.

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