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

With no annotations, the description carries the full burden. It discloses the tool's informational nature and that prices are 'live', implying a non-cached read. However, it doesn't state the return format, whether any side effects occur, or that it's read-only. For a zero-parameter lookup tool, this is adequate but not exhaustive.

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 sentences with no filler. The key content (prices, trial length, card handling, cancellation) is front-loaded, and the usage hint adds value without redundancy. It is efficiently structured and easy to scan.

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 parameterless tool with no output schema or annotations, the description covers the essential information an agent needs: what data is available and the caveat to use live data. It doesn't specify return type or structure, but for a simple lookup this is not a significant gap. The description is sufficient for correct invocation.

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 the baseline is 4. There is nothing to explain about parameters, and the description correctly focuses on the content rather than any input semantics. No additional parameter detail is needed.

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 clearly states the tool retrieves live plan prices, trial length, card handling during trial, and cancellation terms. It specifies the resource (pricing) and the exact content, and the closing phrase 'Read this rather than quoting a price from memory' gives a concrete use case that distinguishes it from estimate-oriented tools like estimate_cost.

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 description implies when to use it: whenever current pricing or trial details are needed, explicitly cautioning against relying on memory. It doesn't name alternatives or exclusions, but the context makes the appropriate use clear, especially given the sibling list includes estimate_cost for estimates.

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