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

The readOnlyHint annotation already communicates safety, so the description adds value by specifying precisely what data is returned: status, timestamps, plan, member, orders, and coupon. It also names the underlying GraphQL query (subscription(id)), which gives the agent extra confidence about the operation's nature.

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 sentences, no filler. The primary purpose is front-loaded and the field list is compact but informative. Every word earns its 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 single-id fetch with one parameter and readOnlyHint set, the description covers the return payload and the underlying operation. It doesn't mention error behavior or what happens if the id doesn't exist, but given the tool's simplicity the definition is sufficiently 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?

The input schema already documents id as 'The subscription id', so the description adds no new semantic detail for the only parameter. With 100% schema coverage, the baseline of 3 is appropriate.

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 verb and resource: 'Fetch one subscription by id', and enumerates the returned fields. This clearly distinguishes it from list_subscriptions, which retrieves many subscriptions, and from memberful_graphql, which is a general-purpose tool.

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 implicitly establishes the primary use case: retrieving a single subscription when its id is known. It doesn't explicitly contrast with sibling tools like list_subscriptions or change_subscription_expiration, but the phrase 'by id' makes the selection criteria apparent.

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