Retrieve a user's retention summary: first/last active dates, active days, streaks, and retention span, to analyze engagement trends.
获取用户留存摘要（首次/最近活跃、活跃天数、连续活跃天数、留存跨度）。
Args:
user_id: 用户 ID（默认 local）
Returns:
{exists, retention: {...}}
| Name | Required | Description | Default |
|---|---|---|---|
| user_id | No | local |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It implies a read-only operation via 获取 (get) and discloses the return structure {exists, retention: {...}}, but it does not cover permissions, 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 description is short and front-loaded: it states the purpose, then lists Args and Returns in a clean structure. Every line earns its place, though the purpose line could be more specific about scope.
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, one-parameter read tool with no output schema, the description provides the essential purpose and a partial return shape. It is minimally adequate but omits usage context relative to siblings and does not explain what 'exists' or the retention fields contain.
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%, but the sole parameter already has a title (User Id) and default (local) in the schema. The description merely restates these as 'user_id: 用户 ID（默认 local）' without adding format or constraint detail, so it does little to compensate for the coverage gap.
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: 获取用户留存摘要 (get user retention summary), and enumerates the metrics included. It does not distinguish this tool from similar siblings such as user_get_activity_stats or user_get_profile, so it falls short of a 5.
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?
There is no guidance on when to use this tool versus alternatives like user_get_activity_stats, nor any prerequisites or exclusions. The description only says what it does, not when to choose it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.