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

Annotations cover the safety profile (idempotent, non-destructive, openWorld), and the description adds genuinely useful behavioral context beyond them: per-call cost ($0.05/call), determinism, primary-source citation, and the billing guarantee that errors and unverified rules are never charged. It stops short of describing rate limits or the output shape, but the pricing/billing disclosure is the key unknown for a paid call.

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?

Three compact sentences, front-loaded with the purpose before cost and correctness claims. Every clause carries information, though the closing billing/guarantee language leans slightly promotional.

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 the schema fully documents all parameters. Combined with annotations covering safety and the description covering cost, determinism, and verification basis, an agent has everything needed to invoke it correctly.

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?

Schema description coverage is 100%, so the schema already documents all seven parameters, including the x_payment header and its unpaid-requirements behavior. The description adds method-level semantics (fees deductible, what counts as a disposal) but no per-parameter syntax or format detail beyond the schema, so baseline 3 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 states a specific computation (Japan crypto-asset realized income) with the two supported cost methods (total_average, moving_average) and defines what counts as a disposal (sell/spend/exchange). This clearly distinguishes it from the other jp_* tax calculators in the sibling list without the agent needing to open any 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?

It names the two available methods but gives no guidance on when to pick total_average vs moving_average, nor any prerequisite or when-not-to-use condition relative to siblings like jp_consumption_tax or jp_retirement_tax. Usage is only implied by the tool's domain.

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