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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, covering the safety profile. The description adds that it returns current/best ratings and win/loss/draw counts, but doesn't discuss rate limits, data freshness, or error behavior. With annotations covering safety, the added context is useful but not rich.

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, front-loaded with the main purpose, and includes practical usage trigger examples. No redundant filler; every sentence 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?

For a one-parameter read-only tool with full annotations and an output schema, the description provides the function, scope, and example usage. It doesn't mention edge cases or limitations, but those aren't critical given the tool's simplicity and rich structured metadata.

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 single 'username' parameter has full schema coverage ('Chess.com username'). The description doesn't add further meaning about parameter format or constraints, so baseline 3 is appropriate.

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?

Description states 'Get a CHESS.COM player's ratings and game records across daily, rapid, blitz, and bullet formats' – a specific verb, resource, and scope. It also includes concrete example queries, making the tool's purpose unmistakable and distinguishing it from generic get_games/get_player tools.

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?

Explicitly says 'PREFER for' with natural language examples, guiding the agent on when to select this tool. It doesn't mention what it should NOT be used for or name alternatives, which keeps it from a 5, but the guidance is clear and actionable.

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