Find friends who own a game

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

The description goes well beyond the readOnlyHint and openWorldHint annotations. It discloses dependencies (STEAM_API_KEY, public friends list), failure modes (found:false, per-friend private_library, rate-limited lookups), caps (100 entries per list, 200-friend lookup limit), and the timeout rationale. This is rich, behavior-critical context.

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?

Though lengthy, the description is tightly packed and front-loaded with the core purpose. Each subsequent sentence addresses a distinct edge case or behavioral caveat, so every sentence earns its place. The structure uses clear separators and comparative language to keep it readable.

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?

Even with an output schema present, the description explains the meaning of key output fields (owners, private_friends, unavailable_friends, friends_checked, total_friends) and truncation behavior. It also covers operational context like timeouts and limits, making it fully complete for agent decision-making.

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 provides 100% coverage for both parameters (appids and steamid), including descriptions. The tool description does not add new parameter-level semantics beyond referencing appids and mentioning source via search_games; it focuses on tool behavior rather than parameter syntax.

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 and resource: 'Check which of a player's Steam friends own one or more games by appid, with each owner's playtime_hours'. It immediately distinguishes itself from get_owned_games and other sibling tools by clarifying scope ('a player's friends' vs 'own ownership').

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?

Explicit guidance is given: 'For the PLAYER'S OWN ownership instead of a friend's, use get_owned_games's check_appids' and 'Get appids from search_games.' It also explains when the tool should not be used or how to interpret missing friends ('treat a friend missing from all three lists as unchecked, not as a non-owner').

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