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

The annotations already declare readOnlyHint=true, destructiveHint=false, and idempotentHint=true, so 'read-only' is repeated rather than new. 'Free' adds cost information beyond the annotations, which is useful, but there is no disclosure of return contents, auth requirements, or rate limits.

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?

The description is two short sentences, with the usage trigger front-loaded. Every clause earns its place, and no filler is present.

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, no-parameter, read-only tool with rich annotations, the description covers the selection trigger and the cost profile. It does not describe the return values, but no output schema exists to carry that either; this is a minor gap rather than a blocking one.

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, so there are no parameter semantics to document. The baseline for a no-parameter tool applies; the schema is complete by virtue of having nothing to describe.

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 precisely: the person's Pugi plan, credit, and today's spend. The verb is implied rather than explicit, but the purpose is clear enough that an agent can distinguish it from unrelated siblings like build_app or buy_credits_link.

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?

It gives an explicit trigger: use when the person asks about their Pugi plan, credit, or what they spent today. It does not name exclusions or alternatives, but the sibling set is largely unrelated, so the routing guidance is sufficient.

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