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

The destructiveHint=true annotation already carries the risk profile, and the description reinforces it with 'MUTATES Memberful data'. Beyond that it adds the underlying GraphQL mutation name (subscriptionChangeExpirationTime), which helps debugging, but it does not say whether the change is reversible, what happens to access immediately upon shortening, or what the response contains.

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, front-loaded with the mutation warning, and every clause carries information: mutation class, effect, unit/type, and the API mapping. Nothing to cut.

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 two-parameter mutation with full schema coverage and no output schema, the description covers what an agent needs to invoke it correctly. It omits any note on return value or error behavior, which is a minor gap given the destructive nature of the call.

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 both id and expiresAt are already documented, including the 'Unix timestamp in SECONDS' note that the description repeats verbatim. The only added value is the GraphQL call signature mapping, which is marginal — baseline 3 is correct.

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 (change) and resource (subscription expiration) and immediately clarifies the semantics: it moves WHEN a subscription expires, extend or shorten. The 'MUTATES Memberful data' prefix cleanly separates it from the read-oriented siblings like memberful_get_subscription and memberful_list_subscriptions.

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?

'Extend or shorten access' gives clear context for the two directions of use and the mutation framing signals this is not a read path. However, it never names an alternative (e.g. memberful_graphql for unsupported expiry mutations) or states any precondition such as requiring an existing subscription id.

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