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

Beyond the annotations, it discloses the widget's actual behavior: one row per player, +N/-N buttons with adjustable step, undo and 20-entry history with round numbers, running totals. It also scopes the tool ("scores stay in the open widget only; no online multiplayer"), which is a genuine persistence/scope constraint the annotations do not express. No conflict with readOnlyHint=true, since the description claims no persistent or external writes.

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?

Front-loads usage triggers, then behavior, then exclusions — a sensible order with no filler. It is a single dense paragraph and slightly long, but each sentence carries selection-relevant content rather than repetition.

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?

With 4 parameters fully documented in schema, an output schema present, and annotations covering safety, the description fills the remaining gaps: widget contents, history depth, player-count bounds, and the sibling routing. An agent has everything needed to decide and call 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 is 100% and the description largely restates what the schema already documents: mode options and default, positive target for target mode, 2-12 players, and starting totals of 0. The sentence about initial player names and starting scores helps orient the agent but adds little beyond the structured fields, so the baseline 3 applies.

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?

States a specific verb+resource — a live scoreboard widget — and immediately differentiates it from both siblings (score_dice_sheet, score_darts_leg) by name. The opening trigger phrases make the resource concrete enough to match against a user request.

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?

Gives explicit positive triggers ("keep score for me and Anna", "scoreboard for game night with 4 players") and an explicit negative case with the two alternative tools to use instead. Nothing about when to select this tool is left to inference.

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