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

With no annotations supplied, the description carries the full disclosure burden and does substantial work: it states the cost ($0.01/call), the payment rail (USDC on Base, eip155:8453), the exact payment field (params._meta['x402/payment']), and the underlying HTTP endpoint. It stops short of describing the response shape (e.g. per-entry added/removed lists) or failure behavior when a snapshot date is unavailable, which keeps it from a 5.

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 definition is front-loaded with the resource and the diff semantics, then the usage rule, then commercials — a sensible order with no wasted preamble. It is docked slightly for redundancy, restating the price twice ('$0.01/call' and 'Price: $0.01 per call in USDC on Base').

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?

For a one-parameter paid x402 endpoint with no output schema and no annotations, the description supplies nearly everything an agent needs to invoke it: the diff semantics, the optional date argument, the payment requirements, and the transport. The only real omission is what a successful diff payload looks like, which matters somewhat given there is no output schema to fall back on.

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% and the single `since` parameter is already documented with its format and default. The description restates 'Pass since=YYYY-MM-DD, or omit for the latest diff,' which reinforces but does not add meaning beyond the schema — the schema already says 'defaults to the previous snapshot.' 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 opens with a specific verb-and-resource definition: a change feed of what was 'added, removed or changed between two daily snapshots' of OFAC sanctions data. The closing line 'instead of re-screening your whole book' implicitly separates it from full-screening siblings like check_sanctions__screen or x402check__check, so an agent can pick it out without opening 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 gives clear operational guidance: poll on a schedule rather than re-screening the whole book, and pass since=YYYY-MM-DD or omit it for the latest diff. The gap is that no sibling tool is named explicitly as the alternative when a full screening is actually needed, so the agent must infer that from the phrase 're-screening your whole book'.

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