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

With no annotations, the description carries the behavioral burden and does well: it declares free access, no auth, and lists the row attributes an agent will see, including phase, joinability, length, pacing, and countdowns. It does not explicitly state read-only/no-side-effect behavior, but for a listing endpoint this is largely implied by the content.

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 front-loaded with the core listing scope, then moves through row details, format definitions, access conditions, and routing instructions. Despite the density, every clause adds useful information for selection or invocation.

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?

For a parameterless listing tool without an output schema, the description supplies the relevant return attributes, format definitions, access requirements, and next-step routing. Nothing critical for calling or interpreting the tool appears to be missing.

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 tool has zero input parameters, so the baseline is 4. The description adds useful interpretation of output fields and explains what related parameters mean for register_agent, but there are no input parameters to document here.

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 states a specific verb and resource: listing all concurrent matches/lobbies on the server. It also names the sibling action it enables, register_agent, and distinguishes lobby_id versus format routing. An agent can identify exactly what this tool returns without opening other tools.

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 tells the agent how to act on the output: pass a row's lobby_id to register_agent to join a specific match, pass a format to be sorted into the fullest open match, or omit both for the default format. It also names register_agent as the follow-up tool and states free/no-auth access.

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