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

Discloses a real behavioral trait not in the annotations: a $0.001 USDC-on-Base cost per successful call via x402, plus the "per successful call" billing condition. The annotations are thin on their own (readOnlyHint=false is odd for a pure lookup) and the description doesn't reconcile that, but the payment disclosure is genuinely useful added context.

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?

Three dense sentences: what it returns, when to use it, what it costs. Zero waste, front-loaded with the resource and field list, with the cost caveat placed last.

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 usefully enumerates the response fields and discloses the payment model, which is what an agent most needs for a paid single-hash lookup. It stops short of stating error behavior when a hash is unknown, though "whether it exists" hints at it.

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 the single parameter is fully documented ("0x transaction hash"), so the schema carries the load; baseline 3. The description adds "by hash" but no additional format or constraint detail beyond 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?

States a precise verb+resource (fetch a Polygon PoS transaction by hash) and enumerates the returned fields (sender, recipient, POL value, nonce, gas limit, selector, block). It does not differentiate itself from the very similar sibling polygon_receipt, so an agent must infer the tx-vs-receipt distinction on its own.

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?

"Use to check what a transaction did or whether it exists" gives clear trigger context for calling it. However, it names no alternatives or exclusions — notably polygon_receipt, which an agent could easily confuse this with — so routing is left partly to inference.

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