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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: it discloses the analytical scope boundary (direct counterparties only, multi-hop requires fund-trace), the risk model (taint by association, both directions), the auth/pricing model ($0.05 per call over x402, x-credit-token header, 1 free call/day, no API key), and what is returned. That is exactly the extra context annotations cannot carry.

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?

Front-loaded with the differentiating question and the sibling contrast, then scope, then payment mechanics. It is long and em-dash heavy, and 'Not financial advice.' is disposable boilerplate, but nearly every remaining clause carries routing or pricing information.

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 paid screening tool with an output schema, the description supplies the scope limit, the alternative and complement tools, the safety annotations, and the full access/pricing model. Nothing an agent needs to decide or invoke is missing.

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 both parameters (wallet, days with default 90/max 365) are already documented in the schema. The description only restates 'Required input: wallet' and adds no format, address-type, or chain constraints. Baseline 3 is appropriate.

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 ('screens a wallet's USDC counterparties against the OFAC SDN list') and explicitly distinguishes itself from the nearest sibling: 'Not "is this address sanctioned" (that's sanctions) but "has it DEALT with one"'. An agent can route correctly without opening either 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?

Names the alternative (sanctions) and the condition that selects it, and gives a complementary-tool rule: 'Covers direct counterparties; pair with fund-trace for the multi-hop funding chain.' It even documents the access path (x402 payment, prepaid header, free tier), which is when-to-use information in a paid-tool ecosystem.

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