Compare two players' libraries

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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses the full-library scanning behavior, the returned-list cap at top 50 by combined playtime, the need to compare `returned` vs `shared_count`, and the self-compare behavior when steamid is omitted. No contradiction with annotations.

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?

Three sentences, each packed with distinct value: purpose, comparison/limitation, prerequisites and self-compare. Front-loaded with the primary purpose, no wasted 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 complexity and existing schema/annotations, the description fully covers selection, behavior, limitations, and edge cases (self-compare, public-profile requirement). The output schema likely handles return-value details, so the description is complete enough.

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. The description repeats the self-compare idea already in schema ('Omit to use the STEAM_ID configured on the server') but adds no new parameter syntax or format details beyond what the schema provides.

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 opens with a specific verb: 'Find games two players both own, with each one's playtime'—clearly identifying the resource (two players' libraries) and differentiating from sibling get_owned_games. It also quotes user intents ('what can my friend and I both play'), making the tool's purpose unmistakable.

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?

It explicitly contrasts with get_owned_games, noting this tool checks full libraries while that caps at top 50, helping agents choose the right tool. It states prerequisites (STEAM_API_KEY, public profiles) and the failure condition (found:false), giving clear when-to-use and when-not-to-use guidance.

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