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

Annotations already declare read-only and non-destructive behavior, but the description adds important operational details: 404 for missing contract, 422 for nonexistent token, both uncharged, plus pricing and failed-call billing. It also clarifies that repeated calls are charged, which is valuable context beyond the annotations.

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?

The description is front-loaded with the core purpose and routing guidance, and the pricing/error details are useful for this paid API. It is somewhat dense, but nearly every clause supports correct invocation or interpretation.

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 states what is returned: the owner wallet plus collection name and symbol. It also covers error behavior and pricing, leaving no critical gap for a two-parameter read-only tool.

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 the two parameters are already documented by the schema. The description adds a concrete example with contract and tokenId, which helps invocation, but it does not add meaningful semantics beyond the schema's own parameter definitions.

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/resource: the owner of one ERC-721 token id on Polygon PoS via ownerOf, plus collection name and symbol. It explicitly distinguishes itself from polygon_nft_balance and polygon_nft_metadata, so an agent can route correctly without opening schemas.

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 concrete use cases: verifying who holds an NFT before a trade, mint gate, or airdrop. It also names the alternatives for count (polygon_nft_balance) and metadata (polygon_nft_metadata), making when-to-use and when-not-to-use explicit.

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