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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial context beyond them: nightly rebuild, data window since 2016, K=64, 1.5x finish weighting, the exact fields returned, and a candid accuracy limitation. This is more behavioral disclosure than most read-only tools provide.

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?

Front-loaded and dense with no filler sentences; the mechanics parenthetical and the log-loss caveat each earn their place. Only minor density cost from packing multiple facts into one sentence.

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 output schema, the description fully compensates by enumerating returned fields for both views, plus data provenance and a fitness-for-purpose caveat. Nothing needed to call it correctly is missing.

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%, so the baseline is 3, but the description adds real meaning: it explains that 'view: card' returns each bout with both ratings, the Elo win probability and the market win probability, and that 'fighters' returns rating/peak/fights/last date/change/weight class. This clarifies what each view actually yields rather than just echoing the enum.

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 and resource: UFC Elo ratings for every active fighter, with the two view modes (fighters vs card) distinguished by content. An agent can separate it from siblings like invoke_mma_projections or invoke_mma_fight_sim without opening the schema.

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?

Gives explicit conditional guidance: because Elo is weaker than the market (log loss 0.671 vs 0.590), it is used only when no odds exist, and the 'card' view is scoped to the next card. It stops short of naming sibling tools such as invoke_mma_odds as the preferred alternative, so routing still takes a small inference step.

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