Cancel Match Lobby

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

Annotations already declare destructiveHint=true, idempotentHint=true, openWorldHint=true, and readOnlyHint=false. The description adds meaningful behavioral context: sign-in requirements, creator-only lobby cancellation, one HTTP attempt, point-read access loss for departing actors, and detailed error semantics. However, it also includes side-effect rules for unrelated operations (start, turn, timeout, active leave), which muddies the transparency for this specific tool.

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 a clear purpose sentence and uses labeled sections, but it is bloated with rules that apply to other tools, such as 'Start requires the creator and every joined UUID exactly once' and 'Turn requires the current unexpired actor.' Those sentences do not earn their place in a description for canceling a match lobby.

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 destructive mutation with no output schema, the description covers authentication, side effects, return shape, and error handling in detail. It is nearly complete for an agent to invoke correctly, with the main weakness being the extra unrelated match-operation rules rather than missing information.

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 description coverage is 100%, so the schema already documents all four parameters. The description nonetheless adds valuable semantics: it explains how sessionToken is obtained from horizon_signin_email or horizon_signin_anonymous, and it stresses that expectedRevision must be the exact original revision and never substituted after an uncertain write.

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: 'Executes cancel match lobby under the exact original revision.' It also distinguishes this action from siblings by noting 'Lobby cancel is creator-only' versus 'Active leave forfeits,' so an agent can tell it apart from horizon_leave_match without opening either schema.

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 provides an explicit 'Use when' section and a 'Not for' list, which is more than most definitions offer. It also names horizon_get_matches and horizon_get_match for reconciliation, though it stops short of directly saying when to choose this over horizon_leave_match.

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