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

Annotations already declare readOnlyHint, idempotentHint and non-destructive behavior, so the safety bar is covered. The description still adds real value by stating no credential is required and that the free tier (1,000 req/month, no card) is included in the result set.

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 compact sentences, front-loaded with the resource and its contents, followed by the use case. No filler or repetition of the title.

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?

With no parameters, no output schema and full annotation coverage, the description is nearly self-sufficient for a simple read tool, telling the agent what fields to expect (quotas, per-minute limits) and the auth situation. Only minor gaps remain, such as whether results are ordered or contain pricing tiers beyond the free plan.

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 zero parameters, so there is nothing for the description to disambiguate. The baseline of 4 applies; the statement that the free plan is always included is a small bonus about fixed behavior.

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 gives a specific verb and resource ("List the UFCalendar Fight API plans") plus the content of each entry: monthly quotas and per-minute limits. It implicitly separates itself from the usage-tracking sibling get_usage by framing the answer as "what does this cost", but it never names that sibling explicitly.

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?

"Answers 'what does this cost' without a credential" tells the agent the exact question this tool resolves and that it works unauthenticated. There is no explicit when-not guidance or named alternative (e.g. get_usage for consumed quota), so it stops short of a 5.

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