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

Annotations already cover read-only, idempotent, and non-destructive. The description adds meaningful context beyond those: the event-replay mechanism, the fact that no wallet or API key is required, and the commercial terms ($0.05 per call over x402 on Base, x-credit-token header for unlimited calls, 1 free call/day). These operational details help an agent decide whether and how to invoke.

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 most important contrast (FULL list vs one wallet) is front-loaded in the first sentence, and every subsequent clause adds a distinct fact: mechanism, output contents, invocation, pricing, auth. A few phrases are promotional ('Compliance-grade visibility no other tool provides') and the pricing block is long relative to the core description, but there is little true waste.

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 needn't be spelled out, and this is a complex tool: two alternative invocation modes, historical replay, per-scope member sets, and commercial terms. The description handles nearly all of that. The noticeable gaps are the zero-required--params case (no guidance on what a no-arg call returns) and 'per scope' being left undefined.

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% but each parameter description is thin ('Registry policy ID' / 'B20 token address'). The description adds the key semantic: the parameters are alternatives ('Pass address= (token) or policy= (registry policy ID)'), an either/or relationship the schema does not convey. It does not clarify what happens if neither optional parameter is passed.

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 precise verb and resource: it 'Replays the Policy Registry's BlocklistUpdated/AllowlistUpdated events into the full membership of a B20's blocklist/allowlist' and enumerates the WHOLE list with history. It explicitly distinguishes itself from b20_freeze_check ('answers one wallet; this enumerates the WHOLE list'), so an agent can tell them apart immediately.

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?

Names the key alternative (b20-frozen-check) and the condition that selects this tool: one wallet's status vs the entire list. It also gives invocation guidance ('Pass address= (token) or policy= (registry policy ID)'). It doesn't address other potentially overlapping siblings like b20_policy_watch or b20_policy_admin, so it's strong but not exhaustive.

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