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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint, so safety is covered; the description adds the useful detail that the response is a pricing catalog with per-call prices. It does not say whether the list is static, plan-dependent, or empty when nothing is paid, which keeps it below a 5.

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, the payload description is front-loaded, and the usage cue comes second. No filler or restatement of the title.

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 parameters and no output schema, the description carries the return-shape burden and does list the fields returned, which is adequate. Minor gaps remain: no note on ordering, paging, or behavior when no paid tools exist.

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 takes zero parameters, so there is no per-argument semantics to explain and the baseline of 4 applies. The description correctly implies no inputs are needed by never referencing any.

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 a specific verb and resource ('Lists every paid tool') plus the exact fields returned (tier, endpoint, price per call). That immediately separates it from the market-data siblings like get_price and coin_profile, which return market data rather than a catalog.

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?

'Call this to see what upgrading unlocks' gives a clear triggering scenario. It stops short of naming exclusions or an alternative (e.g., a free-tier listing tool), so it is clear context without full routing guidance.

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