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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds meaningful context beyond them: the credit cost ('Costs 2 credits'), the ranking method, sort order, and the default active window.

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?

A single dense sentence with the purpose front-loaded ('Use for our fighter ratings'), followed by method, scope, ordering, filter, and cost. No filler; every clause earns its place.

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 need not be described. The description covers method, defaults, filtering, ordering, and cost — enough to call correctly. The only gap is the league parameter, which is documented only in the schema and unmentioned here.

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 baseline is 3, but the description adds value the schema lacks: the default for active_since ('default last year') is stated as behavior, and the weight-class filter and highest-first ordering are clarified. The league enum (mma/pfl/bellator) is not addressed in the description, keeping it from a 5.

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 resource (fighter ratings / Elo) with the exact methodology and scope ('built from the promotion's own results, the UFC since 2000, highest first'). This clearly distinguishes it from siblings like get_fighter, get_leaders, and search_fighters.

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?

Opens with 'Use for our fighter ratings' and gives the default window ('active since a given year, default last year'), which orients usage well. It does not name alternatives or say when NOT to use it (e.g., versus get_leaders), leaving that to inference.

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