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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive closed-world behavior, so the safety profile is covered. The description adds meaningful domain context beyond that: balance is denominated in DELIVERIES rather than money and packs never expire, which materially affects how an agent interprets results.

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 tight sentences with no waste: the first enumerates the returned content, the second supplies a key caveat and a call-to-action. The actionable instruction is front-loaded and easy to parse.

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 output schema, the description carries the burden of explaining what comes back, and it does so: costs, packs, x402 payment requirements, the delivery-based balance unit, and pack expiry. An agent has what it needs to decide whether and how to read the response.

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 is a zero-parameter tool, so the baseline is 4. The description does not try to describe parameters, and its note about balance being counted in deliveries rather than money usefully frames the tool's semantics.

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 exact resources returned: delivery cost, available packs, and the per-pack x402 payment requirements. No sibling tool covers pricing, so it is trivially distinguishable from create_task, get_task, etc.

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 closing directive 'Call this before buying' gives a clear trigger condition for invocation. There is no alternative tool to steer away from, so no exclusions are needed, though it doesn't spell out other cases (e.g. checking balance) where it might also apply.

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