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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered and the description doesn't contradict it. The description adds only that each plan carries prices and inclusions and that plan choice is the owner's decision. It says nothing about authentication (the api_key parameter), pagination, or whether plan data is live or cached.

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, front-loaded with the purpose, and no redundant wording. The elliptical phrasing ('one of them', 'for them') is compact but slightly underspecified rather than wasteful.

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, zero-required-parameter read tool with full annotation coverage and no output schema, the description conveys enough: what is returned (plans with prices and inclusions) and when it matters (picking a plan for a listing). Only the absence of any return-shape or auth detail keeps it from a 5.

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?

There is a single parameter (api_key) with 100% schema description coverage, so the schema already explains everything needed. The description adds no meaning about that parameter, so the baseline of 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?

The description gives a specific verb and resource: 'Listing plans with prices and what each includes', which is clearly a read of a plan catalogue. It falls short of 5 because 'plans' is never grounded (subscription plans for a listing?) and no sibling is named as a contrast, though no sibling in the list is a competing plan-lister.

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?

'A new listing needs one of them' implies the usage context (call this before/while creating a listing), but it is only implied, not stated as an instruction. 'The owner decides, or tells you to decide for them' hints at a decision hand-off but gives no explicit when-to-call, prerequisites, or alternative tools to consider.

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