check_balance

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

No annotations are provided, so the description carries the full burden. It states what the tool checks but doesn't explicitly disclose whether it is read-only, whether it consumes any resources, or if it requires authentication. Given the simplicity, it's likely non-mutating, but this is implied rather than stated. The description adds some value by specifying exactly what is checked, but lacks explicit behavioral guarantees.

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 a single, efficient sentence that front-loads the core action ('Check your nightglass account balance') and immediately details the second element ('remaining screenshot credits'). No unnecessary words or filler. Every word earns its place.

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 parameterless tool with no output schema, the description is nearly complete. It tells an agent what the tool does, and the return value (balance and credits) is implied. It doesn't specify the return format (e.g., JSON structure) but given the trivial nature, this is a minor gap. A 5 would require explicit mention of output format or side effects, which is not critical here.

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 0 parameters and 100% schema coverage, the baseline is 4. The description doesn't need to explain parameters since there are none. It adds context about what the tool checks, but this is more about purpose than parameters. The score reflects that the description is sufficient for a parameterless tool.

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 uses a specific verb ('check') and clearly identifies the resource ('nightglass account balance' and 'remaining screenshot credits'). It inherently distinguishes from the sibling tool 'take_screenshot', which is about capturing screenshots, not checking balances. The purpose is unambiguous.

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?

The description provides clear context by explaining what the tool does, which implicitly tells an agent when to use it (when balance or credit info is needed). It doesn't explicitly mention alternatives or exclusions, but with only one sibling, the distinction is obvious. This falls short of a 5 because it doesn't explicitly state 'use this when you need balance information rather than taking a screenshot'.

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