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

Annotations already declare readOnlyHint=false, destructiveHint=true, idempotentHint=true, openWorldHint=true. The description adds critical behavioral context: it pulls the user into the activity group, doesn't auto-leave on exit, requires user confirmation before proceeding, and 409 conflicts should follow the response body's exits rather than retry. This goes beyond annotations and discloses side effects and error handling. Slight deduction because it doesn't explicitly mention auth requirements beyond '需要登录' (requires login), but that's present.

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 description is well-structured with clear sections: 【需要登录】【何时用】【组合链】【口径/坑】. Every sentence earns its place, covering when to use, related tools, side effects, and error handling. It's dense but organized, front-loading the most important usage context.

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 tool with no output schema, the description covers all necessary context: when to use, prerequisites (login), side effects (group join), error handling (409), and related tools. The combination chain provides a complete workflow. Nothing critical is missing for an agent to call this correctly.

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 schema already documents the single parameter activityRef. The description adds context that activityRef is the slug or id from get_activity / get_signup_activity, which is helpful but not extensive. Baseline 3 is appropriate since schema does the heavy lifting.

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 states a specific verb and resource: '报名免费线上参会' (join free online participation), and clearly explains what it does: users who want to watch live/replay or get materials that are only visible after registration. It distinguishes itself from siblings by noting it's the only free entry point, even for paid events. The title and description align well.

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 explicitly says when to use: when user wants to watch live/replay or get registration-only materials. It also provides a combination chain: get_activity → this tool → list_activity_materials / export_live_messages. It names alternatives like set_conversation_muted and leave_conversation for handling group chat noise, and mentions check_activity_eligibility indirectly via get_activity's canEnterOffline. This is explicit when/when-not guidance.

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