Extend a user's subscription by a specified number of days. Expired users become active with the new period starting now; active users simply gain additional days.
Extend user subscription by N days (expired users become ACTIVE with +N days from now; active users get +N days added)
| Name | Required | Description | Default |
|---|---|---|---|
| days | Yes | Number of days to extend | |
| userId | Yes | User numeric ID |
Changes observed during successful MCP inspections.
v2.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations present, the description carries the full burden of behavior disclosure. It does this well by explicitly stating the state transition for expired users and the additive behavior for active users. This is meaningful context beyond the tool name, though it stops short of mentioning permissions, reversibility, or error conditions.
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 a single sentence that front-loads the verb and object, then packs the key behavioral nuance into a parenthetical. There is no filler, and every clause earns its place.
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 two-parameter mutation with no output schema, the description is nearly complete: it states what happens in both relevant user states and the schema documents the parameters fully. The main omissions are return-value behavior and explicit alternative routing, but these are secondary for this simple tool.
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 both parameters (userId and days) are already fully documented in the input schema. The description adds no extra parameter-level detail, so the baseline 3 is appropriate.
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 uses a specific verb ('extend'), a clear resource ('user subscription'), and a precise scope (single user). It also adds behavioral specificity by distinguishing expired users (become ACTIVE with +N days from now) from active users (get +N days added), which makes it easy to tell apart from bulk sibling tools.
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 operation is clear, but the description provides no explicit guidance on when to choose this tool over alternatives such as users_bulk_extend_expiration or users_bulk_all_extend_expiration. Usage is implied through the singular 'user' and the operation name, but there are no exclusions or routing cues.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.