活动签到。
用户到达活动现场后，通过此工具完成签到。支持手机号/用户ID/签到码三种方式。
Args:
activity_id: 活动 ID
phone: 手机号（用于签到，需与报名时一致）
user_id: 用户 ID（已登录用户）
code: 签到码（现场扫码获取，或主理人提供的签到口令）
Returns:
JSON 字符串，包含签到状态和签到时间
| Name | Required | Description | Default |
|---|---|---|---|
| code | No | ||
| phone | No | ||
| user_id | No | ||
| activity_id | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description must carry the behavioral burden. It states that check-in is completed and returns a JSON string with status/time, but it does not explicitly mention side effects (e.g., marking attendance) or edge-case behavior (e.g., failure on invalid code). The three identification methods are disclosed, but the mutation aspect is implied rather than stated.
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 concise and well-structured: a short purpose statement, a context line, an Args block with per-parameter descriptions, and a Returns line. No fluff or redundancy; every sentence adds value and the key information is front-loaded.
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 low-complexity tool, the description covers the purpose, when to use it, all parameters, and the return format. It could be slightly more explicit that only one identifier (phone/user_id/code) is expected, and it doesn't describe error handling, but the output schema exists and the overall picture is sufficient for an agent to use the tool 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 description coverage is 0%, so the description fully compensates. Each parameter is explained with meaning and usage context ('phone' must match registration, 'code' is from scan or host, etc.). This is significantly more than the schema provides, and an agent can correctly select the appropriate identifier.
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: '活动签到' (activity check-in), and elaborates that it is used when a user arrives at the event site. It clearly distinguishes this from siblings like create_payment or query_activities by naming the action and context, so an agent can immediately tell what the tool does without opening the 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?
The description gives clear context: use this tool when the user has arrived at the activity. It does not explicitly state exclusions or name alternatives, but the scenario is unambiguous enough that an agent can decide when to invoke it. The lack of a 'when not to use' statement prevents a 5.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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