Check merchant

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

Annotations (readOnlyHint=false, openWorldHint=true, idempotentHint=true) are matched and exceeded: the description states it does not send money, sign transactions, or hold keys, that ignored fields are 'not stored,' that the same target is idempotent for 60 seconds, and it quantifies rate limits (100/1,000 per UTC day), overage pricing ($0.001 USDC on Base via x402) and the HTTP 402 payment_not_configured failure mode. This is unusually rich disclosure of side effects, limits, and auth.

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?

Purpose and the primary usage instruction are front-loaded ahead of the caveats, and each paragraph carries distinct information (what it is not, when to call, anti-gaming, scoring limits, billing). It is longer than most tool descriptions and the quota/pricing detail could arguably live in docs, but nothing is pure filler.

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 fully enumerates the return shape (score, verdict, reasons, recommended_action, signals including chain_analysis always not_in_v1, checked_at, policy_version) and covers auth, quota, overage billing, and idempotency. An agent has everything needed to invoke it correctly and interpret the response without further documentation.

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 coverage is 100%, so the baseline is 3, but the description adds real meaning beyond the schema: accepted target formats and the important edge case that an embedded 0x address in a URL scores the host only and will never return trusted. It also documents auth alternatives not in the schema (Authorization: Bearer / X-API-Key) and reinforces that category and amount_usd are ignored.

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 first sentence states a specific verb and resource: 'Decide whether an autonomous agent should pay a merchant, host, or wallet,' and the second names the product and what it returns (a deterministic trust score for one target). It is immediately distinguishable from the siblings get_quota and get_api_key, which the description classifies as billing/quota helpers rather than scoring tools.

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?

Explicit when-to-use ('immediately before a payment, a checkout redirect, or a transfer to a new 0x address') plus explicit negative guidance ('Do not use this tool to execute a payment. Do not use it to overturn a block. Do not call it again with a reworded category, purpose, or amount to fish for a better verdict'). It also states that non-billable helpers exist, routing the agent to the correct alternative for quota/key needs.

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