Get global achievement rates

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

The description adds significant behavioral details beyond the annotations (readOnlyHint, openWorldHint): the output is capped at 200 achievements, the need to check 'returned' vs 'count' to know if all were returned, behavior for unknown appid (empty list instead of error), and that no API key is required. These details are not provided by annotations and are critical for correct invocation.

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 three sentences, each adding essential information. The first sentence clearly states the core purpose, the second explains output details and limitations, the third covers edge cases and additional context. It is front-loaded and contains no extraneous words.

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?

Given the tool's simplicity (single parameter, existing output schema, annotations), the description covers everything an agent needs: return format, limitations, behavior for invalid inputs, source for parameter, and authentication requirements. It is fully complete for the tool's complexity level.

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 input schema already has a description for the appid parameter, achieving 100% coverage. The description reinforces where to get the appid (search_games) and adds that the tool works without a key, which is relevant for the parameter's usage. This adds some value beyond the schema, but the schema already sufficiently explains the parameter, so a score of 4 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?

The description precisely states the tool's function: 'Get the global unlock percentage of each achievement in a game by appid'. It clearly identifies the resource (achievements), action (get unlock percent), and scope (by appid). It also distinguishes itself from the sibling tool get_game_achievements by explicitly noting that this tool returns internal names and unlock percents, not display names/descriptions, thus preventing confusion.

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 provides explicit guidance: when to use this tool (to get unlock percentages), when to use an alternative (for display names/descriptions, use get_game_achievements), how to obtain the required appid (from search_games), behavior for invalid inputs (empty list, not error), and that it works without a key. This covers both when and when-not to use the tool.

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