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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint, so the safety profile is covered. The description adds value beyond that by mapping to the underlying action (action=members.lookup) and by interpreting the result ('found=false means they are not a member yet'), though it does not describe pagination, rate limits, or error behavior.

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?

The critical instruction ('ALWAYS call this before registering') and the read-only note are front-loaded, which is the right ordering. The fully duplicated Korean text adds length without new information for a single reader, a minor cost against an otherwise tight structure.

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 correctly steps in to explain the return semantics (found=false). Combined with the read-only flag, action id, and 100%-covered two-parameter schema, an agent has enough to call it correctly; only error/edge-case handling is left unstated.

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% and both parameters (email, agent_id) are documented in the schema, including the audit-trail purpose of agent_id. The description adds no parameter-level detail beyond the schema, 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 and resource: checking whether a 'star365 unified member' exists for a given email. It also pins down the scope precisely enough to separate it from member_register and members_cross_platform, which the sibling list shows are distinct operations.

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?

Explicitly instructs 'ALWAYS call this before registering' and explains why (avoiding duplicate person creation in delegated signup). This gives the agent both the trigger condition and the failure mode it is guarding against, which is the strongest form of when-to-use guidance.

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