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

Discloses live data reading, advises against caching, explains the price format (whole minor units), and clarifies that empty credit packs are expected ('that is the answer, not a fault'). This goes far beyond the readOnlyHint annotation, which only indicates a safe read operation. It gives the agent confident expectations about freshness, formatting, and edge cases.

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?

Four sentences that front-load the main purpose, then logically cover usage trigger, price formatting, caching guidance, and the empty-credit-pack caveat. Every sentence earns its place; there is no filler or redundancy. The structure is easy to scan and understand.

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 zero-parameter read-only tool with no output schema, the description covers the critical return information: prices, limits, price format, credit packs, and per-action costs. It also explains the live nature of the data. It does not list exact field names or the exact structure of the plan object, but it provides enough for an agent to interpret the response correctly.

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 tool has zero parameters, so there are no parameter meanings to explain. Per the calibration baseline, a zero-parameter tool earns a 4 because the schema is trivially complete and the description cannot add parameter-specific value. The description instead focuses on output semantics, which 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?

States 'Return Gemalli's current subscription plans with their prices and limits, read live from the platform.' This clearly identifies the action (return), resource (subscription plans), and source (live from platform). The title 'Plans and prices' reinforces the purpose, and none of the sibling tools (products, manufacturers, categories, etc.) overlap, so it is well differentiated.

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?

Explicitly says 'Use it when the person asks what Gemalli costs or what a plan includes.' This gives a clear trigger condition. It also adds practical advice about formatting prices and not caching. It does not mention alternatives or when not to use it, but no alternatives are relevant among the siblings, so this is a minor gap.

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