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

With no annotations, the description carries the full burden. It does disclose two behavioral facts an agent cares about: the key's plan and the live rate-limit counter, implying a read-only, identity-scoped call. It does not state that it has no side effects, nor what auth context it assumes.

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?

A single short sentence with no filler, and the most useful fact (plan + quota) is front-loaded. It is slightly clipped as a verbless fragment, which costs a little clarity.

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?

The tool is simple (no params, no nested objects), but with no annotations and no output schema the description should fully describe the response shape and side-effect profile. It names the two returned data points but not their structure or any auth/read-only guarantee.

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 schema defines zero parameters, so there is nothing for the description to clarify; the baseline for a no-parameter tool is 4.

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 concrete resource it returns: the plan tied to the current key plus the remaining per-minute call quota. That is specific enough to separate it from all siblings (app/keyword search tools), though it is a noun phrase with no explicit verb like 'returns' or 'reports'.

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?

There is no guidance on when to call this versus anything else, nor any stated prerequisites (e.g., that a valid key must be configured). The agent must infer usage entirely from the name.

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