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

The readOnlyHint annotation already declares this is a read operation, and the description aligns with that by using 'Get'. It adds the useful behavioral detail that related resources can optionally be embedded via 'zoom', but it does not disclose behavior like not-found responses or how zoom affects the payload beyond what the schema hints.

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, no filler. The core purpose ('Get a single subscription by id') is front-loaded, and the endpoint reference provides useful context without bloating the text.

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 simple read tool with only two parameters, this is largely complete: it names the resource, the identifying parameter, the optional zoom behavior, and the underlying endpoint. It does not describe return shape or error cases, but the readOnlyHint and straightforward GET semantics make this a minor gap.

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?

The schema already covers both parameters with descriptions, so the description is not required to add much. The phrase 'optionally zooming related resources' loosely maps to the zoom parameter, but it adds no extra meaning beyond the schema's own description and example.

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 ('Get'), a specific resource ('a single subscription'), and the selection mechanism ('by id'), clearly distinguishing it from foxy_list_subscriptions and foxy_update_subscription. The mention of optional 'zoom' behavior further clarifies its scope.

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?

It clearly implies this tool is for retrieving one subscription by its id, and the context of the Foxy hAPI endpoint reinforces that. It does not explicitly name alternatives like list_subscriptions or update_subscription, but the single-resource framing gives enough context for an agent to choose it over listing or updating.

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