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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered; the description adds genuine value with the negative contract 'Never returns an install code', which prevents a common wrong assumption about the response payload. It does not discuss polling cadence, error behavior for an unknown order_ref, or how long states take to transition.

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?

Two short sentences, zero filler, with the state list up front and the payload exclusion as a closing caveat. Every clause carries information the agent needs.

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?

With no output schema, the description takes on the job of describing return values and does so by naming the four status values, plus flagging the install-code omission. It is slightly under-complete in that 'ready in NUM' is opaque and the broader response shape beyond status is unstated.

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?

There is a single parameter at 100% schema description coverage, so the baseline is 3. The description's mention that the order was started with esim_start_checkout echoes what the schema already states for order_ref, adding no new syntax, format, or sourcing detail.

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?

A specific verb (check) plus resource (order status) tied explicitly to the sibling that creates the order, esim_start_checkout. It goes further by enumerating the possible states (waiting for verification, waiting for payment, paid, ready in NUM), so an agent knows exactly what the tool reports and how it differs from esim_find_plans and esim_start_checkout.

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 clearly anchors usage to orders already started via esim_start_checkout, which tells the agent this is a post-checkout tool and not a discovery tool. It lacks an explicit when-not statement or a pointer to whichever sibling would supply the install code it says it never returns, leaving that inference to the agent.

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