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

Annotations already state readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds that relationships can optionally be embedded, which is useful response-shaping context, but it does not describe auth needs, error behavior, or rate limits. With annotations covering the core traits, a 3 is appropriate.

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 front-loaded sentence followed by the endpoint, with no wasted words. It immediately conveys the core purpose and optional relationship embedding. Both elements earn their 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 simple get-by-id tool with full schema coverage and annotations covering safety, the description is nearly complete. It states the resource and optional embed behavior. It could mention return shape or not-found behavior since there is no output schema, but the missing detail is minor.

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 schema already documents both parameters. The description adds value by enumerating usable relationship names for the 'with' parameter (customer, billing, term, product, address, orders, shipments, logs), beyond the generic pattern in the schema. This meaningfully improves parameter interpretation.

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 resource and scope: 'One subscription by id,' distinguishing it from list_subscriptions and other resource getters. The endpoint 'GET /v1/subscriptions/{sub_id}/' reinforces the retrieval purpose. An agent can identify this as a single-subscription fetch without ambiguity.

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 implies usage when a specific subscription id is known and relationships may be embedded, but it does not explicitly say when to use this tool versus list_subscriptions or other alternatives. No exclusions or preconditions are stated. This is minimum-viable implied guidance.

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