credits_balance

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 genuinely new behavioral fact — that the call is free — but says nothing about whether the value is live or cached, or about any rate limiting on repeated polling.

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 fragments, front-loaded with the resource and followed by the cost note. Nothing is wasted, though the extreme terseness leaves room for a clarifying clause at no real length cost.

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, an existing output schema, and annotations covering safety, the definition is functionally sufficient to call the tool. It stops short of explaining what a credit represents or when the balance matters, leaving an agent without context for interpreting or acting on the result.

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 nothing for the description to disambiguate beyond what the empty schema already conveys. Baseline 4 applies.

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 resource and what it reports: the remaining credit balance on the KeyFlint license. An agent can identify it as a balance-lookup tool immediately. It does not differentiate itself from the adjacent 'pricing' sibling, which is the one tool an agent might plausibly confuse it with.

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 — the 'Remaining credits' framing suggests calling it to check a balance, and 'Free' hints it can be called without consuming credits. There is no explicit when-to-use statement, no prerequisite, and no comparison to alternatives such as 'pricing'.

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