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

Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds the auth requirement ('No key required'), which is a behavioral trait not covered by annotations. This is exactly the kind of contextual value the rubric rewards.

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 no redundancy. The resource is front-loaded, and the auth note is separated into its own sentence. Every word earns its place.

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 endpoint with no output schema, the description covers the resource content ('plans and per-tier limits') and auth requirements. It does not describe the exact output format, but that is not essential for an agent to successfully invoke the tool.

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?

This tool has zero parameters, and the description correctly implies no inputs are needed. With 0 params, the baseline is 4; there is no parameter information the description would need to add.

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 names the resource ('the plans and per-tier limits') and gives concrete detail (free, dev, pro), making it clear this returns pricing/plan data. It lacks an explicit verb like 'get', but the noun phrase is unambiguous and distinct from all sibling tools.

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 'No key required' note gives a clear usage signal: this endpoint is accessible without authentication, unlike many siblings. However, it does not explicitly state when to choose this tool over alternatives or when not to use it; the usage context is implied rather than stated.

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