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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds the underlying HTTP method and path, which signals a simple scoped read, but says nothing about pagination, result limits, or whether inactive/canceled subscriptions are included.

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 with the purpose front-loaded and the API mapping secondary. No filler, though it is quite terse for a list operation.

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?

Adequate for a one-parameter read with annotations covering safety, but on a list endpoint the absence of any note on pagination or result scope leaves a minor gap. No output schema exists, so return-shape information would have helped.

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?

Only one parameter and schema coverage is 100%, so the schema fully documents external_customer_id. The description adds no format or semantics beyond what the schema provides; baseline 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 clear verb (List) and resource (a customer's subscriptions), and the API endpoint reinforces the exact scope. It does not explicitly differentiate from the close sibling lago_get_subscription (singular) or lago_list_subscriptions (all subscriptions), but the 'a customer's' qualifier does most of that work.

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?

No guidance on when to use this versus lago_get_subscription for a single subscription or lago_list_subscriptions for the full list. The API mapping implies read-only retrieval but no conditions or exclusions are stated.

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