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

It explicitly labels the operation as a WRITE, describes the partial-update semantics, tells the agent the call returns a request_id, and gives the underlying endpoint. Annotations already flag destructiveHint and idempotentHint, so this adds useful context, though it does not warn about what mutation of list membership or customdata entails.

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?

Three short sentences with no filler; the WRITE marker and the field list are front-loaded, then the partial-update rule, then the return value and endpoint.

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 an 8-parameter mutation with nested objects and no output schema, the description covers operation type, partial-update behavior, return value (request_id), and scope. Minor gaps remain around how list membership and customdata entries merge on update.

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 only 25%, yet the description enumerates the semantics of the optional fields (contact detail fields plus custom data and list membership) that the schema leaves undocumented. It does not explain nested details like whether list_names appends or replaces, but it compensates well for the low coverage.

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 names a specific verb (change) and the exact editable fields (name, email, mobile, landline, custom data, list membership) on a subscription resource, so it is clearly distinguishable from sibling create/read tools like trumpia_add_subscriptions and trumpia_get_subscription.

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?

"Only the fields you pass change" clearly establishes the partial-update use case, but the description does not say when to prefer this over trumpia_add_subscriptions or how it relates to cancel/get operations, so usage context is implied rather than spelled out.

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