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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely non-obvious behavior: multi-platform searches return only games supporting crossplay across all listed platforms, results are capped at 10 sorted by popularity, and the total match count is returned alongside the page. The trailing "Read-only" merely restates the annotation and earns no credit.

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-loaded with the use case, then catalog scope, filter behavior, and return shape in a tight sequence. Every sentence carries information except the final "Read-only", which duplicates the annotations and could be dropped.

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?

There is no output schema, and the description compensates by spelling out the return contents (page url, platforms, online/same-screen counts, crossplay, price), ordering, cap and total count. For a 9-parameter read-only search tool, an agent has everything needed to call it and interpret the result.

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 already 89%, so the baseline is 3. The description goes beyond it by explaining the AND-combination rule and, critically, the intersection semantics of the platforms array — an agent would not infer from the schema that passing several platforms filters to games with crossplay between all of them.

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 and resource ("find games" in CoopGames' co-op/multiplayer catalog) and anchors it with a concrete scenario ("3 friends, one on PS5 and one on Xbox"). It explicitly separates itself from the sibling get_game, so an agent can route correctly 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?

Gives an explicit when-to-use condition ("when you don't have a specific game in mind") and names the alternative for the opposite case ("For one known game use get_game instead"). It also states that all filters are optional and combine with AND, which is the key invocation guidance for a zero-required-parameter tool.

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