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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered. The description adds genuinely new behavioral context: it returns 'Facts, never a verdict' (no recommendation is synthesized), and some fields are sport-conditional ('best projected lineup change (NFL)'). It does not say what happens when a player is unresolvable or how per-provider gaps are handled.

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?

One front-loaded sentence with zero filler, and the source-vs-facts distinction is placed at the end where it lands as a qualifier. The mid-sentence catalogue is telegraphic and takes effort to parse, costing it the top mark.

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 10 parameters, nested credentials, and no output schema, the description's job is to convey what comes back — and it enumerates the returned facts precisely (ownership, points, projections, age, contract, injury, lineup delta, roster spots, pick ownership). Combined with 100% schema coverage on inputs, an agent has enough to call it and anticipate the payload.

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 description coverage is 100%, so the schema already carries get/give/provider/league_id/team_query/credentials semantics. The description adds only indirect hints (NFL-specific lineup output, Sleeper-only pick ownership), which implies provider/sport dependencies but gives no parameter-level guidance beyond what the schema states. Baseline 3.

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 ('Check a proposed trade') plus an explicit scope constraint ('in ONE league'), then enumerates the exact facts returned (rosters, points, projections, age, contract, injury, lineup change, pick ownership). No sibling tool claims this territory, so an agent can route to it unambiguously.

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 'ONE league' scoping and the pointer 'news via fantasy_get_player_data' tell the agent what this tool does not cover and where to go instead. There is no explicit statement of when not to call it (e.g. pre-draft, or a league that isn't connected), so it stops short of full when/when-not guidance.

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