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

The annotations already declare readOnlyHint=true, so the safe-read profile is covered. The description adds the pagination trait and the underlying endpoint, which is modest additional context but says nothing about return shape, ordering, or defaults.

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 operation front-loaded and no filler. The 'Lago API: GET /plans' line is arguably redundant for an agent but is compact and not detrimental.

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 read-only list tool with full schema coverage and readOnly annotations, little is left unspecified. The lack of any note on return format is acceptable given the tool's simplicity and the absence of an output schema.

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 description coverage is 100%, so page and per_page are already documented in the schema. The description's 'paginated' nod confirms intent but adds no format, default, or boundary detail 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 specific verb (List) and resource (billing plans), and the 'paginated' qualifier clarifies the operation scope. It implicitly distinguishes from lago_get_plan by the plural listing verb, but never names the sibling to reinforce the distinction.

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 intent is implied by 'List billing plans,' so an agent can infer this is the enumerate-all operation. However, there is no explicit when-to-use guidance, no mention of alternatives like lago_get_plan for a single plan, and no excluded cases.

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