pricing

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds one behavioral fact — 'Free' — suggesting calling this tool costs no credits, which is genuinely useful context, but it is ambiguous (free tool vs. free credits) and says nothing about rate limits or how prices are kept current.

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 front-loaded fragments with no wasted words. The terseness does cost some precision — 'Free.' is a bare fragment whose referent is unclear — but structure is efficient.

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?

An output schema exists, so return values need not be described, and a parameterless informational tool has little else to specify. The remaining gap is the ambiguity of the pricing units and of 'Free', which a slightly fuller sentence could resolve.

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 the baseline is 4; with nothing to document, the schema and description together are sufficient. No meaningful parameter context is missing.

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 a specific resource (credit price of each tool) and a secondary output (where to buy credits), which is distinguishable from the sibling credits_balance that reports a balance rather than prices. It is telegraphic but an agent can tell what it returns without reading the schema.

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?

Usage is only implied: an agent would consult this to learn per-tool credit costs or where to top up. There is no explicit when-to-use statement, no mention of credits_balance as the alternative for checking remaining credits, and no stated prerequisites.

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