Account plan and credits

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

The readOnlyHint annotation already ensures the agent knows it's safe. The description adds context about the specific information returned and the operational purpose (monitoring credits), which is useful beyond the annotation.

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, tightly packed with purpose and usage guidance. No filler words, and the most important information (what it shows) is first.

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 simple, read-only tool with no parameters and no output schema, the description fully communicates what the agent will receive (plan and credits) and why to use it. It is complete for the tool's complexity.

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?

With zero parameters, the schema is fully covered; the description adds context about what the tool accesses (the API key's plan and credits) rather than parameter syntax, which is not needed. Baseline for 0 params 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 clearly states a specific verb ('Show') and resource ('this API key's plan and remaining query/scan credits'). It is distinct from sibling tools, which all perform lookups or searches, not account-level information queries.

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 advises to 'Check this before running credit-consuming operations,' which tells the agent when to use this tool and why. Though no alternative tool is named, the guidance is clear and actionable.

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