Get current player count

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

The description adds meaningful behavioral context beyond the annotations: it notes 'No API key required' (authentication requirement) and 'Errors clearly if the appid is unknown/invalid rather than returning a null count' (error handling behavior). These details are not provided by annotations, so the description enhances transparency.

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 two sentences with no filler. It front-loads the primary purpose, then adds necessary prerequisite and error behavior in a compact manner.

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 (one param, no nested objects) and comes with an output schema, so the description does not need to explain return values. The description covers purpose, prerequisite, authentication, and error handling, making it complete for an agent to use correctly.

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 for the single parameter 'appid' is 100%, and the schema already describes it as a Steam application id with a reference to search_games. The tool description repeats this guidance without adding new semantic value beyond what schema provides, 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?

The description clearly states the tool's function: 'Get how many people are playing a game right now (live concurrent player count) by appid.' This is a specific verb-resource pair with clear scope, and it clearly distinguishes itself from sibling tools like get_game or get_prices.

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 context for when to use this tool ('right now') and includes a cross-reference to 'Get the appid from search_games' for obtaining the required parameter. However, it does not explicitly state when not to use the tool or list alternatives, so it falls short of full exclusionary guidance.

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