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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context by stating no credential is required and enumerating the specific content (quotas, limits, trial terms), but it does not go further into response format or data source details.

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?

Two concise sentences with no filler. The main action and content list are front-loaded, and the practical use-case statement ('answers what does this cost without a credential') adds value without redundancy.

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 parameterless, read-only, idempotent tool, the description fully covers what the agent needs to know: what the tool lists, the quota-related content, and that no credential is required. No output schema exists, but the described return content is simple enough to infer.

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, so the schema is already complete and there is no parameter ambiguity. The description further clarifies that no credential is needed, which effectively communicates the absence of auth-related 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 names a specific verb ('List') and a specific resource (UFCalendar Fight API plans), and details exactly what is returned: monthly request quotas, per-minute limits, and no-card trial terms. It also distinguishes this from costing/credential-related use cases, making it clear among siblings like get_usage.

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 gives a clear use case: answer 'what does this cost' without a credential. It implies this tool is appropriate when no authentication is available and the agent needs plan/quotas information, though it does not explicitly name alternative tools or state when not to use it.

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