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

With annotations present, the description goes further by explaining WHY readOnlyHint=false: each call appends an immutable record to a public ledger (implying non-idempotence, matching idempotentHint=false), and clarifies the tool moves no funds. It also adds verifiability details (SHA-256, public ledger, verify_url) not present in 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?

The critical non-payment disclaimer is usefully front-loaded, but the text is long and largely duplicated across Japanese and English, restating the same points (no payment execution, ledger append, parallel layers). The core value is buried under repeated framing, so structure is adequate but not tight.

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 annotations plus description cover safety profile, side effects, and verifiability. Given the tool's moderate complexity, it is nearly complete; only error behavior and the precise meaning of the appended ledger record are left implicit.

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 three parameters. The description's mentions of quoted_price (within/above/below verdict) and merchant (not used for judgment) largely restate what the schema properties already state, adding no new syntax or format guidance. 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 verb and artifact ('issues a FairPriceAttestation' that a shopping/payments agent attaches to a Cart Mandate) and explicitly scopes what it does NOT do (no payment initiation/authorization/execution, no fund movement). This separates it cleanly from siblings like verify_fair_price and get_fair_price_sources, which verify or source prices rather than mint an attestation record.

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 gives a clear usage context ('Bridge for AP2 agents ... attach to a Cart Mandate before asking the user to sign') and notes that quoted_price triggers a fair-range verdict. It does not explicitly name which sibling to use instead when the agent only wants to verify a price, so it stops short of full when/when-not routing.

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