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

Beyond the readOnly/idempotent/destructive annotations it discloses rich behavior: attacker-controlled on-chain strings flagged untrusted_content:true and never fetched, malformed node answers producing an uncharged 5xx, 0.3-2 s latency, USD 0.002 price and a shared 10-read/day free pool. This is exactly the context annotations cannot carry.

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?

Dense but well ordered: purpose, inputs, returns, security caveat, error/latency, then pricing and free tier. Length is justified because most sentences carry new operational facts, though it does restate the parameter formats already in the schema.

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 fully enumerates the return fields (standard, interfaces, name/symbol, owner, exists, token_uri plus truncation/resolution variants) and adds safety, error and cost context, leaving nothing an agent needs to call it 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 each parameter already documents its format (enum for chain, 0x+40 hex contract, uint256 decimal/0x-hex token_id). The description largely restates those formats without adding new meaning, so baseline 3 applies.

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 ('read one NFT') with an explicit scope of Ethereum or Base, and the title narrows it to standard, owner and token URI. This distinguishes it from fungible-token siblings like get_token_info and generic scans like scan_contract_address.

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?

The description makes the use case clear (reading a single NFT's standard/owner/URI) and surfaces chain limitations, pricing and the shared free-tier pool. However, it never names an alternative or states when NOT to use it, e.g. vs get_token_info or get_portfolio, so alternatives must be inferred.

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