Pay: subscriptions events

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

The description restates read-only (consistent with readOnlyHint=true) and, more usefully, discloses the return shape — time, event type, source, status change, summary — which no output schema provides. It stops short of stating ordering, volume, or retention limits for the event history, so it is not fully transparent.

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-loaded and short, with the purpose in the first clause and the routing advice last. The opening two sentences partially restate each other ('Show the lifecycle history' / 'Returns a subscription's lifecycle history'), a small redundancy that keeps it out of the top band.

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 single-parameter read tool with no output schema and annotations already covering safety, the description supplies everything missing: what an event row contains, that the call is non-mutating, and when to reach for it versus the mutation siblings.

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% and the single 'id' parameter is already documented in the schema, including the hint to obtain it via pay_subscriptions_list. The description adds no extra meaning about the id beyond what the schema says, 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?

The description gives a specific verb and resource ('Show the lifecycle history of a subscription') and then specifies the granularity of the result ('one row per event'), which separates it from the sibling pay_subscriptions_get / pay_subscriptions_list. An agent can tell what this tool returns without opening the 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?

It states both a positive use case ('check it to explain a subscription's state') and a temporal condition relative to concretely named alternatives (use before pay_subscriptions_cancel, pay_subscriptions_resync, pay_subscriptions_relink). This is explicit when-to-use guidance with named siblings, which is exactly what routing requires.

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