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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds value beyond annotations by specifying what the tool returns and by flagging that crypto and Telegram Stars are in beta testing, which sets appropriate expectations.

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 a single front-loaded sentence with a colon-separated enumeration of payment options. It conveys the scope, the beta caveat, and the extra current-term field with no filler or repetition.

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, one-parameter tool with an output schema and annotations, the description is largely complete. The only meaningful gap is not clarifying when the agent should prefer get_instance_term for the term portion, but that is more of a usage-routing concern than a missing invocation detail.

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 input schema covers the only parameter, id, with 100% coverage and already explains that it is the instance id returned by create_instance or list_instances. The description adds no additional parameter-level meaning, so the baseline score of 3 is appropriate.

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 names a specific verb and resource: 'Get ways to pay for an instance's plan', and enumerates the returned categories (card/subscription buy links, crypto, Telegram Stars, current term). It is clear, but it does not explicitly differentiate itself from the sibling get_instance_term even though the description also returns the instance's current term.

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?

There is no explicit guidance about when to use this tool versus alternatives, and no mention of when not to use it. The overlap with get_instance_term could confuse an agent, and the description does not address that or any other routing considerations.

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