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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so safety is covered. The description adds only the 'GET /plans' endpoint, which is essentially restated by those annotations – it says nothing about pagination behavior, auth requirements, or rate limits.

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 fragments, front-loaded with the purpose and the returned fields. The trailing 'GET /plans' endpoint is largely redundant with the tool name, but nothing is verbose or buried.

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?

With no output schema, enumerating the returned plan fields is genuinely useful, but the description omits the pagination envelope (next_page is referenced by the page param in the schema) and any indication of filtering/sorting support. Adequate but incomplete for a list tool with nested filter objects.

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% and all five params (page, sort, filter, per_page, updated_after) are fully documented in the schema. The description adds no parameter detail, so the 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?

Clear verb+resource: 'List subscription plans' with an enumerated set of returned fields. It is distinguishable from invoiced_get_plan by the plural 'list' vs singular 'get', though the description never names that sibling explicitly to sharpen the contrast.

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 statement of when to use this versus invoiced_get_plan, invoiced_list_subscriptions, or other list siblings, and no prerequisites or filtering guidance. The agent must infer usage purely from the name.

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