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

Annotations already declare read-only, non-destructive, open-world; the description adds real context beyond them: 404 with no charge for unknown hashes, $0.01/call via x402 USDC or card key, first 25 free, failed calls free, and no caching benefit since repeats are charged.

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 purpose and fields, then alternatives, then input format, then pricing. Dense but nearly every clause carries information; the pricing tail is long but operationally relevant given per-call charging.

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?

No output schema exists, but the description enumerates the returned fields (sender, recipient, value in POL, nonce, gas limit, selector, block), so an agent knows what it will get, and error behavior and cost are covered.

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 format is already documented; the description reinforces it with the exact 0x-prefixed 64-hex requirement and a concrete worked example hash, which aids correct invocation.

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 ("Look up a Polygon PoS transaction by hash") and enumerates the returned fields, making it clearly distinct from polygon_receipt and polygon_logs, 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?

Gives explicit when-to-use ("see what was sent or whether it exists") and names the alternatives with their conditions: polygon_receipt for success/failure and fees, polygon_logs for emitted events.

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