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

Annotations already provide the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false). The description adds non-obvious behavioral context beyond that: substring matching over names and emails, and rate-limiting imposed by the platform to deter scraping. This is useful operational information.

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?

Three sentences, each earning its place: the main action, the motivating use case, and a rate-limit caution. The verb and resource are front-loaded, and there is no filler or redundant 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?

For a single-parameter, read-only search tool with an output schema present, the description covers what the tool does, why an agent would use it, and a key operational caveat. Nothing an agent needs to decide whether to call it 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 description coverage is 100%: the query parameter is documented as 'Substring to search names and emails against.' The description essentially restates this scope, only adding that the search targets the 'play user directory.' With high schema coverage, the description need not add much parameter-level detail.

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 opens with a specific verb and resource: 'Search the play user directory by name or email substring.' This clearly identifies the tool as a lookup operation and distinguishes it from sibling tools like play_send_friend_request or play_list_my_friends, since it is the discovery step rather than the action step.

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?

The description states a concrete use case: 'Used to locate a user before sending a friend request.' This gives clear context for when to call the tool. It does not explicitly name alternatives or exclusions, but the intended position in the friend-request workflow is unambiguous.

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