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

Beyond the annotations, which already mark readOnlyHint and idempotentHint, the description adds a crucial domain-specific behavior: 'does not consume a Signal.' This is non-obvious and materially affects how an agent should treat the call, since signal consumption is likely a limited resource. It also discloses the response contents (balances, allowance, Stripe credit), giving full behavioral transparency.

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, front-loaded sentence that first states the action, then the key details, then the read-only caveat. There is no redundant wording or filler; every clause adds information.

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 zero-parameter, read-only access check with an output schema present, the description covers all necessary aspects: what it checks, what it doesn't do, and its safety profile. The output schema handles return-value details, so no further elaboration is required.

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 has zero parameters, so there is no parameter semantics to explain. The description adds meaningful context about what the access check reports, which is more than sufficient for a parameterless tool. The baseline of 4 for 0 parameters 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?

The description uses a specific verb ('Checks') and clearly enumerates the resource and data points: complimentary and paid Signal balances, whether analysis can run, which allowance is used next, and the latest Stripe purchase. This makes the tool's function immediately distinguishable from its siblings, which analyze opportunities or purchase signals.

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 conveys clear context: it is a read-only status/pre-flight check that tells the agent whether analysis can run and which allowance will be used, strongly implying it should be called before analyse_small_business_opportunities or purchase_marginglow_signal. It does not explicitly name alternatives or state when not to use it, so it stops short of a 5.

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