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

Annotations declare the safety profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false, openWorld=true), so the description's real value-add is the pricing ($0.02/call), the determinism guarantee, source citation, and the notable no-charge-on-error/unverified-rule policy. That is concrete behavioral context an agent could not derive from the annotations.

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?

One dense sentence fragment with the core analysis front-loaded, followed by pricing and reliability terms. Every clause carries information; only the parenthetical threshold pair could be trimmed, and no filler is present.

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-value explanation is unnecessary, and the description covers scope, cost and reliability. Gaps are minor: supported rule years/jurisdiction scope and the x402 payment flow (which is documented in the schema rather than the description) are not restated.

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 fully documents year, as_of, x_payment and annual_income_yen — baseline 3. The 1.06M/1.30M figures in the description add interpretable meaning about what thresholds the income value is tested against, but no format or constraint detail beyond the schema.

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 analysis (income-wall analysis) over a named domain: Japanese tax, social insurance (1.06M/1.30M) and spousal/student-dependent thresholds. An agent can distinguish it from jp_social_insurance or jp_payroll_net by the 'walls' framing, but the description never names those siblings to sharpen the distinction.

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 characterizes the domain of the computation but gives no when-to-use or when-not guidance and names no alternatives among the many jp_* calculation siblings. Cost and billing behavior are covered, but tool selection is left entirely to inference from the topic.

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