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

No annotations are provided, so the description carries the full behavioral disclosure burden. It does this well by specifying that no authentication is required and by detailing the returned data shape and units. While it does not discuss pagination or edge cases like an empty plan list, those are minor for a simple public listing tool.

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 entire description is one efficient sentence with the verb and resource front-loaded, followed by a compact enumeration of return attributes. It contains no filler, repetition, or irrelevant context, and every clause adds useful information for invoking and interpreting the tool.

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 zero-parameter, no-output-schema, no-annotation tool, this description is complete: it identifies the resource, the public scope, the exact return fields, the units, and the authentication requirement. An agent has all the information needed to decide to call it and to interpret its result 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?

The tool has zero parameters, and the schema confirms no required or optional properties. According to the calibration baseline for zero-parameter tools, the description needs no additional parameter explanation. The description's focus on return fields is appropriate given there is nothing to document about inputs.

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 uses a specific verb ('List') with a clear resource ('FlexYield's public subscription plans'), making it immediately obvious what the tool does. It further enumerates the exact fields returned, including prices in integer USD cents, billing interval, quota, and burst limits, which strongly distinguishes it from other list_* siblings. No ambiguity remains about the tool's purpose.

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 makes clear this is a public, read-only listing operation requiring no authentication, which provides solid context for when an agent should invoke it. It does not explicitly name alternative tools or state when not to use it, but for a parameterless public plan-listing tool the use case is clear and there are no obvious competing siblings.

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