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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the agent knows this is a safe read operation. The description adds the constraint that it only returns public data (published OPL ratings) and excludes private fields, which is useful context beyond the annotations. However, the description does not disclose behavior like error handling for non-existent usernames or rate limits. With annotations covering the safety profile, a 3 is fair.

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?

The description is a single, tight sentence that front-loads the core purpose ('Look up an exact public username and published OPL ratings') and then lists exclusions. Every word earns its place, with no fluff. This is an excellently concise and well-structured description.

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?

The tool is simple with only one parameter, and the annotations provide the safety profile (read-only, idempotent). The description covers the scope and exclusions, and there is no output schema needed to explain return values (the description says it returns OPL ratings). For a lookup tool of this complexity, nothing essential is missing, making it complete.

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 0%, so the description must compensate. The description specifies that 'username' must be an exact public username, and that it is used to look up published OPL ratings. This adds meaning beyond the schema's pattern (which just says string of letters/numbers/.-_ up to 64 chars). It clarifies the semantics of the parameter, justifying a 4.

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?

The description clearly states the verb (look up), the resource (public player rating), and the exact scope (exact public username, published OPL ratings). It also explicitly lists what is not included (email, telephone, location, match history, private fields), which distinguishes it from potential sibling tools like search_myopl_help or search_myopl_website. This is a specific and unambiguous definition.

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 description implies when to use this tool: when you need public OPL ratings for an exact username. It does not explicitly name alternative tools or provide when-not-to-use guidance, but given the sibling list (search tools, browse tools), the restriction to 'exact public username' and 'published OPL ratings' gives clear context. A 4 is appropriate because it is clear but lacks explicit exclusions.

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