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

Annotations already cover read-only, idempotent, non-destructive and closed-world, so the bar is low; the description still adds real signal by enumerating returned content and, more usefully, disclosing failure behavior ('unknown slugs and classic ports return an error and no play link'). It stops short of any auth/quota context but that is minor for a public read 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?

Two tight sentences; the lookup key and its derivation come first, then return payload, then error semantics. No filler, no restatement of the title.

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 carries the return-value burden and does so by listing the fields returned plus the error/no-play-link case. Nothing an agent needs to call this single-parameter tool correctly is 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?

Schema coverage is 100%, so the baseline is 3, and the description earns above baseline by defining the slug semantically as 'the last segment of https://zadely.com/games/<slug>/', which tells the agent how to derive it rather than only how to format it.

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 ('look up') plus resource ('one AI-made browser game') and the exact lookup key ('by its Zadely slug'). The word 'one' plus slug-keyed lookup implicitly separates it from the sibling list/search/random tools, so an agent can route correctly without opening another 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?

Usage is implied rather than stated: the tool is for when you already have an exact slug, and the note that 'unknown slugs... return an error' warns the agent that fuzzy or partial input will fail. However, it never names an alternative ('use search_games if you only have a name'), so the boundary with search_games must be inferred.

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