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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), so the bar is lower. The description adds genuinely useful behavior the annotations do not: provenance (events replayed from the Policy Registry), historical attribution ('when, by whom'), and cost/auth model ($0.05 per call via x402 on Base, x-credit-token for unlimited calls, no API key, no free tier). Mostly strong, though the 'compliance-grade visibility no other tool provides' line is promotional rather than behavioral.

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 key differentiator is front-loaded and the structure is logical. However, it is dense and includes filler ('Compliance-grade visibility no other tool provides'), and the pricing/auth detail trails at the end rather than being tighter.

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 no explanation. The description covers purpose, the competing sibling, both parameter options, and the payment/auth model — everything an agent needs to invoke it correctly for a read-only, two-optional-param tool.

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 schema descriptions are bare ('Registry policy ID (optional)', 'B20 token address') and omit the relationship between the two. The description clarifies that either address= or policy= selects the same resource, which is real added meaning.

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+resource: replaying BlocklistUpdated/AllowlistUpdated events to enumerate the full membership of a B20's blocklist/allowlist, including attribution and current member set. It explicitly contrasts itself with b20_freeze_check ('answers one wallet; this enumerates the WHOLE list'), so an agent can disambiguate without opening a 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 alternative tool and the condition that selects it: use b20_freeze_check for a single wallet, use this for the whole list. It also states which parameter form to pass (address= for a token, policy= for a registry policy ID). Routing is fully explicit.

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