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

Goes well beyond annotations: explains the malformed-address path (400, uncharged), pricing model ($0.003/call via x402 USDC or card key, first 25 free, failed calls free), and explicitly reconciles the surprising readOnlyHint=false with the reason (per-call charging). This is exactly the context annotations cannot convey.

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 outcome, then usage, then error/pricing detail. Four clauses pack a lot without filler, though the billing sentence is dense and could be trimmed for an agent that only needs the call semantics.

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 enumerates what comes back (bytecode size, EIP-1167 status, implementation address), and covers errors, cost, and the annotation rationale. Nothing material for calling it correctly 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 coverage is 100% so the baseline is 3, and the description adds a concrete example address plus the malformed-input behavior (400, uncharged), which the schema does not state. Slightly above baseline, though the address format itself is left to the schema.

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?

Specific verb (check) plus resource (0x address on Polygon PoS) and the exact output dimensions: bytecode size, EIP-1167 minimal-proxy detection, and implementation target. It is clearly distinguishable from sibling polygon_* tools and from check_counterparty, which it names.

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?

States the triggering context ('before sending funds or approving a spender') and routes to the alternative ('for a fuller risk verdict use check_counterparty'). Both when-to-use and which-sibling are explicit.

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