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

Annotations already cover read-only/open-world, so the description adds real value beyond them: the data source (public rankings page), the content boundary (no fight records), and a precise billing model ($0.002 USDC per successful call via x402; failed calls uncharged). That pricing/charging detail is exactly the kind of behavioral context an agent needs before invoking. It stops short of describing pagination or freshness of rankings.

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 sentences, both front-loaded: content/scope first, then source boundary and cost. No filler, and the disqualifying clause ('no fight records') arrives before the pricing detail rather than buried.

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?

An output schema exists so return values needn't be explained, and the description covers source, scope, exclusions, and cost. It doesn't address ranking freshness/update cadence or whether a division substring that matches multiple divisions returns all matches, which is the main remaining ambiguity for a two-param read tool.

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?

Schema coverage is 100% and both parameters are documented there, including the 1–15 limit and the division substring example, so the baseline is 3. The description adds no parameter-level meaning beyond restating that results are divided by division; the mention of rank number and athlete page link describes output, not 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?

States a specific verb+resource+scope: official UFC.com athlete rankings by division, with champion and ranked athletes including rank number and athlete link. It also excludes what it is not ('no fight records or per-fight stats'), which implicitly separates it from dev_ufcstats and dev_espn_mma, though it never names those siblings.

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?

Usage is implied by the content ('rankings by division'), and the exclusion of fight records hints at when to pick a stats tool instead. But there is no explicit when-to-use guidance, no named alternative, and no statement of prerequisites beyond the payment mechanism.

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