Pay: subscriptions get

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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description reinforces 'Read-only'. With no output schema, the description adds genuine value by disclosing the returned fields (status, price, customer email/name, billing period, trial end, cancellation dates, reference, checkout URL). It stops short of noting pagination or error behavior, but a single-id lookup has little to disclose there.

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 tight sentences, front-loaded with the core action and scope, then the field list, then the sibling routing note. No filler sentences; every clause carries information.

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 read tool with one fully-documented parameter and no output schema, the description covers the essentials and compensates for the missing return schema by listing the fields returned. It could be stronger by clarifying where the id comes from in-flow, but it is essentially complete.

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 description coverage is 100% and the schema already documents the single `id` parameter as a guid found via pay_subscriptions_list. The description restates 'by id (guid)' without adding syntax or format detail, so the baseline of 3 applies.

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 ('Show one subscription by id (guid)') and then enumerates the exact fields returned, so an agent knows precisely what it gets. It also names the sibling `pay_subscriptions_events` as the contrasting tool, disambiguating it from the 'get' family.

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 clear context for use (fetch a single subscription by guid) and an explicit alternative for a related need ('for how it got into this state use pay_subscriptions_events'). It does not, however, route to sibling reads like pay_subscriptions_list or pay_subscriptions_by_user, leaving some sibling selection to inference.

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