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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, and the description adds materially: 'Reads or computes only and changes nothing', explicit pricing ($0.01/call via x402 USDC or card key), a 25-call free tier, failed calls free, and the warning that 'each call is charged, so repeats are not free' — which coherently explains the idempotentHint=false annotation in billing terms. This is behavior an agent needs before calling a paid tool and cannot get from structured fields alone.

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?

It is front-loaded with the purpose and outputs, and most sentences carry distinct load (networks, cost, use case, example, safety). The block is dense and the pricing/billing clause is slightly buried after the chain list, but nothing is pure filler.

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?

There is no output schema, so the description must describe the return values — and it does so field by field (owner, metadata, holdings, collection contract and proxy status). Combined with the chain scope, cost model and read-only/side-effect disclosure, an agent has everything needed to decide and invoke correctly.

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 schema already documents chain, tokenId and contract, so the baseline is 3. The description adds a concrete worked example (contract=0xC36442b4a4522E871399CD717aBDD847Ab11FE88, tokenId=1) and reiterates the ERC-721 / five-chain constraint, giving usable format guidance 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?

The description names a specific verb and resource ('One call to analyse an NFT') and then enumerates exactly what is returned: current owner, metadata fields and their source schemes (data:, https, ipfs), collection holdings count for that owner, and collection contract name/symbol/proxy status. It also states the supported networks and ERC-721 scope, which cleanly separates it from the per-chain siblings like eth_nft_owner or base_nft_metadata.

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?

It gives a clear usage context ('Use before buying, listing or verifying an NFT') and points at the alternative it replaces ('Cheaper than the tools bought one by one'), which maps onto the many per-chain nft_* siblings. It does not state any when-not-to-use condition, so it falls short of full alternative routing.

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