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

Goes well beyond the annotations by disclosing pricing ($0.125 per call), the x402/MPP payment handshake, that validation happens before any charge, and that a P0 bearer key switches the tool to making the paid call itself. That is unusually rich behavioral context for a readOnly/idempotent tool. Minor gap: it does not say what happens on partial match results or what the per-call charge is when screening fewer than 25 addresses.

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 usage trigger, then the mechanics and pricing, then the sibling routing – good ordering. It is a single dense paragraph with a long embedded key-purchase URL that slightly hurts scannability, but nearly every clause carries actionable 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?

With no output schema, the description still explains what comes back ('the exact paid x402 request…with the response schema and an example') and how to complete the call. Combined with the single fully documented parameter, an agent has everything needed to invoke it correctly in either payment mode.

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 there is only one parameter, so the baseline is 3; the description nonetheless adds meaning by naming accepted chain formats and reiterating that names are rejected. It does not add format details (e.g. checksum/case requirements) beyond what the schema says.

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 specific verb and resource ('screen a list of wallet addresses against sanctions lists') plus concrete scope ('up to 25 per POST', supported chains 0x/BTC/TRX/SOL). It explicitly names the sibling it is not, sanctions_screening, so an agent can select between them 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?

Opens with an explicit trigger ('Use when you need to screen a list...in one call') and gives the exclusion plus alternative routing: 'For one address or a name use sanctions_screening.' It also covers the P0 key branch, telling the agent which mode applies when.

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