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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=false) by disclosing the billable nature, that the call is refused once the plan allowance is exhausted, that the station starts AVAILABLE, and that it cannot be launched until a flow is chosen. This is exactly the kind of consequence and auth/limit context the annotations cannot express.

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?

Front-loads the virtual-vs-native distinction and the billable warning, and every sentence carries distinct information (creation state, billing limit, flowSrcId caveat). It is on the long side and occasionally emphatic ('and must not try'), but nothing is redundant padding.

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 mutation tool with no output schema, it covers what the agent needs: cost/refusal behavior, required confirmation with the merchant, and the post-creation instruction to have the merchant pick a flow in Run → Stations. No material gap remains.

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 baseline is 3, but the description adds real meaning for flowSrcId: it is the POS layout the till runs, the wizard treats it as mandatory, no tool lists flows, and the station is unlaunchable until one is set. That is genuine semantic value beyond the schema, though name and outletId are left to the schema.

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 ('Add a VIRTUAL till — a browser-based station') and immediately distinguishes it from what it is not ('You CANNOT create a native (device) station from here'). This lets an agent separate it from siblings like hub_delete_station, hub_rename_station, and hub_get_stations without opening a 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?

Gives explicit when-to-use and when-not-to-use guidance: virtual tills here, native tills self-enrol via the POS app. It also surfaces the gating condition (billing allowance) and the prerequisite workflow for flowSrcId, naming the alternative path (cabinet wizard) where no listing tool exists.

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