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

Adds substantial context beyond annotations: data: URI / https / ipfs.io resolution paths, truncation of strings over 1,000 characters, 422 (uncharged) for a nonexistent token, and metadataError for unreachable metadata. The note that each call is charged also explains why idempotentHint is false, which the annotation alone would leave opaque.

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?

Purpose and identity are front-loaded in the first clause, and the pricing/error details arrive after. It is dense but nearly every sentence carries actionable information; the billing tail is slightly long for a read-only lookup.

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 spells out what is returned (tokenURI and the parsed JSON fields), plus error and truncation semantics. Nothing an agent needs to call it or interpret a response 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 schema already defines both parameters, giving a baseline of 3. The description adds a concrete worked example (contract=0xC364...FE88, tokenId=1) and clarifies tokenId refers to a single ERC-721 token, which reduces format guesswork.

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+resource: 'the token URI of one ERC-721 token id (tokenURI) and the JSON it points to (name, description, image, attributes)'. It also names the sibling it is not (polygon_nft_owner), so an agent can route 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?

States explicitly 'Use to show or check what an NFT is; for its owner use polygon_nft_owner', giving both the use case and the alternative. It also flags cost per call and that repeats are not free, which informs when to avoid redundant calls.

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