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

Annotations already cover safety (readOnlyHint, idempotentHint, destructiveHint false), so the bar is lower, yet the description adds genuinely new behavior: a long-poll that blocks for up to 25 seconds when 'since' is supplied. That timeout is the key trait an agent needs and it is not in the annotations or schema.

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?

Two sentences, zero filler: the first front-loads what the call returns, the second states the polling contract. Every clause earns its place.

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 no output schema, the description sensibly enumerates what the view contains (cards, board, turn, available actions), which is what an agent needs here. It could be more explicit that the response is what supplies the next 'since' version, which is the crux of the polling loop, but coverage is otherwise adequate for a 2-parameter tool.

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 both 'since' and 'api_key'. The description restates the 'since' semantics ('the version from your last view') without adding format or syntax beyond what the schema says, so the baseline of 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?

The description names a concrete resource and its payload ('your view of the match: your cards, the board, whose turn it is and what you can do'), which clearly separates it from action tools like make_move or make_move's siblings. It stops short of naming a sibling it is not, but the resource description is specific enough for an agent to route correctly.

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 gives one clear usage rule: pass 'since' from your last view and the call blocks up to 25 seconds for a change. It never states the alternative case (calling without 'since' for an immediate snapshot) or when to prefer another tool, so usage is implied rather than spelled out.

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